Anatomy

Question 1

Thoracic plane

Answer 1

• runs from manubriosternal joint/angle of Louis to inferior endplate of T4
• division of superior and inferior mediastinum
• structures transected:
  
  • bifurcation of trachea
  • aortic arch (inner cavity)
  • just above pulmonary trunk bifurcation
  • azygos drains into SVC, arching over right main bronchus
  • left recurrent laryngeal nerve loops around aortic arch
  • thoracic duct moves from right to left hand side posterior to oesophagus
  • ligamentum arteriosum with RLN recurring beneath it
  • cardiac plexus (superficial and deep parts)
  • termination of prevertebral fascia (fuses with anterior longitudinal ligament) and pretracheal fascia (blends into fibrous pericrdium)

(CLAP TRAP: cardiac plexus, ligamentum arteriosum, aortic arch (inner concavity), pulmonary trunk, tracheal bifurcation, right to left movement of thoracic duct, azygos drains into SVC, pre-vertebral fascia and pretracheal fascia end)

Question 2

Transpyloric plane

Answer 2

• Halfway between sternal notch and pubic symphysis
• Or intersection of linea semilunaris with costal margin at level of 9th costal cartilage
• Structures:
  
  • L1
  • Pylorus
  • D1
  • DJ flexure
  • Gallbladder fundus
  • Neck and body of pancreas
  • Confluence of splenic vein with SMV
  • SMA origin
  • Root of transverse colon mesentery
  • Left and right colic flexures
  • Spleen
  • Hilum left kidney
  • Upper pole of right kidney
  • Tips of 9th costal cartilages
  • Termination of spinal cord

Question 3

Transtubercular plane

Answer 3

• Plane uniting two tubercles of iliac crest (these are slightly posterior and superior to ASISs along iliac crest)
• Structures at transtubercular plane:
  
  • L5
  • Start of IVC, 2.5cm right of midline

Question 4

Axilla

Answer 4

• pyramidal area through which neurovascular structures pass between the root of the neck and the arm
• boundaries
  
  • base = convex axillary skin/where angular veins drain into thoracodorsal vein
  • apex = narrow communication between clavicle in front and first rib behind - defined by the costoclavicular ligament (Halsted ligament); at which point the axillary vein becomes the subclavian vein
  • posterior: subscapularis above, lat dorsi and teres major below
  • medial: serratus anterior
  • lateral: intertubercular groove of humerus
  • anterior: pec major, pec minor, clavipectoral fascia, subclavius
• nerves - brachial plexus
• vasculature
  
  • axillary artery
    
    • divided into 3 parts by pec minor (prox/post/distal to)
    • cords of brachial plexus named by relationship to 2nd part of artery
    • lateral margin of 1st rib to border of teres major
    • branches: STLSAP (sixties teens love sex and pot)
      
      • superior thoracic
      • thoracoacromial
      • lateral thoracic
      • subscapular (becomes thoracodorsal after giving off circumflex scapular)
      • anterior circumflex humeral
      • posterior circumflex humeral
  • axillary vein
• lymphatics
  
  • medial side of axillary vein
  • level I-III according to relationship with pec minor (lateral, posterior, medial to it up to Halsted’s ligment)

Question 5

Brachial plexus

Answer 5

• Formed by the ventral rami of nerve ROOTS C5-T1 which are behind the scalene muscles and give off:
  
  • dorsal scapular nerve C5 (rhomboids & levator scapulae)
  • nerve to subclavius C5,6
  • long thoracic nerve C5,6,7
• TRUNKS - superior, middle, inferior
  
  • emerge between scalenus anterior and medius
  • cross posterior triangle, over first rib, behind subclavian artery
  • upper and middle lie above SCA, lower lies directly on its superior surface
  • covered by skin, deep fascia and platysma
  • crossed by suprascapular nerve, EJV and inf belly omohyoid
  • superior gives off suprascapular nerve, C5,6
• DIVISIONS
  
  • each trunk branches into anterior and posterior divisions
  • posterior to middle third of clavicle
• CORDS - medial, lateral, posterior
  
  • posterior divisions unite to form posterior cord, upper 2 anterior divisions unite to form lateral and lowermost anterior divison forms medial cord
  • formed in cervicoaxillary canal, surround 2nd part of axillary artery
    
    • first part: medial cord is posterior, lateral and posterior cords are lateral
    • second part: take up positions indicated by names
  • lateral cord
    
    • lateral pectoral C5,6,7 (pec major)
  • posterior cord
    
    • upper subscapular C5,6 (subscapularis)
    • lower subscapular C5,6 (subscap and TM)
    • thoracodorsal C6,7,8 (lat dorsi)
  • medial cord
    
    • medial pectoral C8,1 (pec major & minor)
    • medial cutaneous nerve of arm T1
    • medial cutaneous nerve of forearm C8
• TERMINAL BRANCHES
  
  • lateral cord
    
    • musculocutaneous nerve C5,6,7
  • posterior cord
    
    • axillary nerve C5,6
    • radial nerve C5,6,7,8,T1
  • lateral and medial cord
    
    • median nerve C5,6,7,8,T1
  • medial cord
    
    • ulnar nerve C8,T1

Question 6

Breast

Answer 6

• modified sweat gland of ectodermal and mesodermal origin
• base lies between ribs 2-6; sternal edge to MAL
• overlies pec major superomedially and to a lesser extent the serratus anterior inferolaterally and EOM below and medially
• glandular appendage of skin therefore contined within superficial fascia; deep surface abuts deep fascia overlying pec major and serratus interior
  
  • between pec fascia and deep layer of superficial fascia = retromammary space - rel avascular
• consists of 15-20 lobules of glandular tissue of varying size with varying amounts of adipose tissue between the lobules; no distinct fascial compartmentalisation
• fascial bands run from deep layer of the superficial fascia to skin between duct lobular units; together w skin envelope support weight of breast
• breast lobules are placed more peripherally in the breast and drain into small ductules that coalesce into larger (lactiferous) ducts individually draining each main lobule
  
  • 15-20 lactiferous ducts/lobular units open individually onto NAC
  • each duct has a subareolar dilatation (infundibulum) that collects milk during lactation for suckling
• retro-areolar space contains smooth muscle, but no subcut fat
• UOQ has greatest proportion of glandular tissue, hence increased incidence of breast ca here
• while most breast tissue is superficial to deep fascia, lobular tissue often extends along lateral border of pec major and deeply into the axilla
  
  • this is the breast’s axillary tail and the glandular tissue can reach as far as ax vein
• blood supply - PILL(s)
  
  • pectoral branch of thoracoacromial (2nd part of ax artery)
  • internal mammary (from subclavian near its origin) - paramedian plane 1-2mm from midline between internal thoracic and transverse thoracic muscles
    
    • perforators in 2nd-5th ICS + branches to skin
    • divides into musculocutaneous & superficial epigstric in 6th ICS
  • lateral thoracic artery (from 2nd part ax artery at lat margin of pec minor, runs down lat border of pec minor & sends branches around lateral border of pec major into breast (ext mammary branch)
    
    • also supplies serratus anterior, pec muscles, subscap
  • lateral branches of posterior intercostal vessels - perforate serratus anterior anterolaterally
  • +/- branches of subscapular artery
• venous drainage
  
  • follows arterial supply
  • superficial veins form extensive anastomotic network & assume a circular configuration around nipple ‘circulus venosus’
  • deep veins drain almost entirely into axilla
  • a valveless, venous plexus surrounding vertebrae extends from base of skull to sacrum & is in direct communication w posterior intercostal arteries; this connection provides potential pathway for mets to vertebral column & CNS
• lymphatic drainage
  
  • 75% to axilla; 25% to int mammaries
  • in 5% predominant drainage is to IM
• innervation
  
  • sensory innervation from intercostal nerves 2-6 and in part from supraclavicular nerve
  • retroareolar space has layer of smooth muscle - somatic & autonomic excitation contraction of these fibres –> erection of nipple & decrease in diameter of areola

Question 7

Chest wall

Answer 7

The muscular layers of the thorax can be divided into those that are within the chest wall, and those that surround it.

• Chest wall:
  
  • External intercostal (same orientation as external oblique)
  • Internal intercostal (same orientation as internal oblique)
  • The innermost layer is broken into three components; the subcostal, the innermost intercostal, and the transversus thoracis.
• Surrounding muscles
  
  • Anteriorly;
    
    • Pectoralis major; sweeping origin from clavicle, sternum, upper 6 cc, and external oblique
    • Pectoralis minor; arises from ribs 3-5 and inserts into corocoid process
    • External oblique; arises from lower 8 ribs interdigitating with serratus
    • Rectus abdominis taking origin from the 5th, 6th, and 7th costal cartilages.
  • Laterally;
    
    • Serratus anterior; arising from the upper 8 ribs and inserting into scapula
  • Posteriorly
    
    • Rhomboids minor (C7 and T1) and major (T2-T5) inserting medial border scapula
    • Trapezius with its sweeping origin from all cervical and thoracic vertebrae and SP
    • Latissimus dorsi from the lowermost 3-4 ribs and SP of the lower 6 thoracic vertebrae

Question 8

Diaphragm

Answer 8

• a domed, fibromuscular sheet that separates the thoracic & abdominal cavities
  
  • it is active on inspiration - accounts for 70% of insipration w 5cm of movement; passive on expiration
    
    • right dome ascends in exp to 4th space; left to 5th rib
  • contraction aids that of abdominal wall in raising intra-abdo pressure w straining
• arises from:
  
  • upper lumbar vertebrae via the crura
    
    • right L1-3 & intervening discs; left L1-2
  • from fascial arches known as median, medial and lateral arcute ligaments
    
    • median = from sides of body of L1 (arches up so coeliac trunk comes off underneath at T12)
    • medial = from side of body of L1 to transverse process of L1 at lateral margin of psoas
    • lateral = from TP to tips of 21th ribs
  • inner sides of lowest 6th rib (tip of 12th, forwards to 11th & each rib to 7th costal cartilage)
  • posterior surface of xiphoid (T8)
  • central tendon w its one anterior and two posterior parts
• openings
  
  • T8 = caval opening - IVC, right phrenic
  • T10 = oesophageal opening - oesoph, vagus nerves, oesophageal branches of left gastric artery & vein, lymphatics
    
    • 2.5cm to left of midline, oesophagus encircled by right crus
  • T12 = aortic opening - strictly behind diaphragm (median arcuate ligament)
    
    • azygos vein, thoracic duct (begins from cisterna chyli), aorta
  • behind medial arcuate ligament - sympathetic trunk
  • behind lateral arcuate ligament - subcostal neurovasc bundle
• things that go through diaphragm/crus
  
  • left phrenic through left hemidiaphragm
  • left hemiazygos through each crus
  • greater, lesser, least splanchnic nerves through each crus
  • extraperitoneal lymph vessels on abdo surface pass through diaphragm to LNs on thoracic surface, mainly in posterior mediastinum
• relations
  
  • superior: pericardium, basal lung segments
  • inferior: right - liver, adrenal, kidney; left - stomach, spleen, adrenal, kidney
  • posterior - azygos, thoracic trunk, aorta, oesophagus, vagus nerves, pleural folds
• blood supply
  
  • right and left inferior phrenic arteries which arise from aorta just beow diaphragm
  • superior phrenic arteries which are smaller arising from aorta in thorax
  • musculophrenic & pericardiophrenic arteries which are terminal branches of internal thoracic arteries
  • costal margin supplied by lower 5 subcostal & intercostal arteries
• nerve supply
  
  • phrenic nerve; each half of diaphragm is supplied by its own phrenic nerve & fibres of right crus that loop to left around oesophageal opening are supplied by left phrenic
  • on reaching abdo surface of diaphragm, both nerves divide into ant, lat & post branches which run radially giving off branches that enter muscle from below
  • 1/3 of phrenic nerve is sensory to heart & pleura, and peritoneum beneath

Question 9

Abdominal wall

Answer 9

The 3 layers of the anterolateral body wall are separate in the flanks, where they are known as external oblique, internal oblique, and transversus abdominis. Towards the midline the layers fuse forming a broad aponeurosis. In the midline the three muscular layers fused in the embryo to form the rectus abdominis. Skin and subcutaneous tissue cover these muscles.

External oblique; arises from 8 lower rib interdigitations; sharing origin with serratus anterior for 4 ribs and latissimus dorsi for 4 ribs. It inserts onto the anterior half of the iliac crest (free border) and a wide aponeurosis.

Internal oblique; arises from the thoracolumbar fascia, the anterior two thirds of the iliac crest, and the lateral two thirds of the inguinal ligament. Inserts onto the 7th-9th costal cartilages and into the aponeurosis. Inferiorly it contributes to the conjoint tendon.

Transversus abdominis; arises from the thoracolumbar fascia, the anterior two thirds of the iliac crest, the lateral third of the inguinal ligament. Contributes to the aponeurosis of the midline and, inferiorly, the conjoint tendon.

Rectus abdominis; has three origins; the pubic tubercle, the pubic symphysis, and pubic crest. Inserts into the 5th, 6th, and 7th costal cartilages and the xiphoid. Has tendinous intersections attached to the anterior sheath.

The central/midline aponeurosis is made from the six laminae of the anterior and posterior fascia for each of the three muscles. Internal oblique splits to enclose rectus above the arcuate line (an inch below umbilicus). Inferior to this point, all the layers pass anteriorly leaving only transversalis fascia over peritoneum; a fact utilised in TEPP hernia repair.

The muscles and skin of the abdominal wall are largely supplied by the lower 6 thoracic nerves and the subcostal nerves. Some innervation is derived from the iliohypogastric and ilioinguinal nerves inferiorly.

Question 10

Anal canal

Answer 10

• Overview
  
  • last 3-4cm of alimentary tract - extends from pelvic floor/anorectal ring to anal verge
  • muscles of anal canal + configuration of mucous membrane are involved in continence; hold the anal canal closed except during the passage fo flatus & faeces
  • puborectalis part of levator ani clasps gut & angles it forwards
  • from this angled junction w the rectum, 2.5cm in front of tip of coccyx, anal canal passes downwards & backwards towards skin of perineum
• Muscles
  
  • tube of muscle like rest of gut but fibres all circular, consisting of int and ext anal sphincters (visceral & skeletal muscle respectively)
  • tube within a funnel - upper parts of funnel = levator ani muscle; stem of funnel = ext sphincter continuous w levator ani; inner tube = int sphincter, continuous with inner circular layer of rectal muscle
  • int anal sphincter - extends along 3/4 length of the anal canal so termintes ~1.5cm below dentate line, just below ext sphincter at intersphincteric groove
    
    • accounts for 85% resting tone
  • longitudinal muscle continuous w outer layer of rectum becomes fibroelastic at anorectal junction & forms conjoint longitudinal coat (separates int and ext sphincters & forms medial edge of intersphincteric space)
    
    • some fibres fan laterally through ext sphincter & insert into perianal skin (corrugator cutis ani muscle)
    • some traverse int sphincter (towards dentate line) & support int haemorrhoids at mucosal suspensory ligs
  • ext sphincter = elliptical
    
    • 3 parts - deep, superficial, subcutaneous
    • deep = continuous w puborectalis except in midline at front where no levator ani fibres
    • middle = elliptical, attached to tip of coccyx at back (contributes to anococcygela lig) and to perineal body at front
    • subcut = circular ring which at lower ends curves below int sphincter
• Mucosa
  
  • at anorectal junction = columnar epithelium w goblet cells (rectal type)
  • anal transformation zone extends from prox anal canal to dentate line
  • below dentate line = pecten (smooth pale area between dentate line & anal verge - non-keratinised stratified squamous epithelium w/o hair/sweat glands)
  • below anal verge (junction of anal mucosa & perianal skin/mucocutaneous junction/roughly corresponds to intersphicnteric groove) = true cutaneous area - hairy skin with sweat & sebaceous glands - keratinised stratified squamous epithelium
  • in upper anal canal = submucous anal cushions @ 3,7,11 o’clock
    
    • consist of fibroepithelial/fibroelastic connective tissue, smooth muscle, dilated venous spaces & arteriovenous anastomoses
  • in upper third of canal, mucous membrane shows 6-10 longitudinal ridges, the anal columns
    
    • at their lower ends, adjacent anal columns are joined together by small horizontal folds, the anal valves - at dentate line
    • pockets formed above anal valves = anal sinuses, into which open mucus sectreting anal glands
    • about half anal glands are submucosal & rest penetrate through int sphincter
  • NB anal margin = vague term; some define as within 5cm of anal verge ie perianal region
    
    • perianal cancers = tumours that arise within the skin at or distal to squamous mucocutaneous junction, that can be seen in their entirety w gentle traction on buttocks & that are within 5cm of anus (previously called anal margin tumours)
    • anal canal tumours = those that cant be seen in their entirety when gentle traction placed on buttocks
• Relations
  
  • posteiror: coccyx; laterally: ischiorectal fossa; anteirorly: perineal body & vagina or urethra
  • spaces
    
    • superficial postanal space = superficial to anococcygeal ligament
    • deep postanal space = between anococcygeal ligament and levator ani muscle - continuous laterally w each ischioanal space and when infected can create horseshoe abscess
    • supralevator space = above levator ani, below and posterior to rectum, and anterior/superior to sacrum; can extend into retroperitoneum
• Blood supply
  
  • superior rectal artery supplies mucosa to dentate line
  • middle & inf rectal arteries (from int iliac and from pudendal branch of int iliac) supply sphincter muscles & lower anal mucosa
  • venous drainage: into portal (proximally) & systemic (distal) circulations
• Nerve supply
  
  • ext anal sphincter: inferior rectal branch of pudendal nerve S2-4)
    
    • pudendal nerve leaves pelvis through greater part of sciatic notch, where it passes under piriformis muscle; then crosses ischial spine & sacrospinous ligament to enter ischiorectal fossa through lesser sciatic foramen via pudendal/Alcock’s canal
    • pudendal nerve has 2 branches: inferior rectal nerve (supplies ext anal sphincter & sensory supply from 1-2cm above pectinate line downwards); and perineal nerve (innervates ant perineal muscles & urethral sphincter and forms dorsal nerve of clitoris (for penis)
  • puborectalis: mainly from direct branch of S4 nerve root but may derive some from pudendal nerve
  • levator ani: S3 and 4
  • autonomic supply to anal canal & pelvic foor from 2 sources
    
    • sympathetic = L5 nerve root sends sympathetic fibres to sup & inf hypogastric plexuses
    • parasympathetic supply = from S2-4 nerve roots via nervi erigentes
    • fibres of both systems pass obliquely across lateral surface of lower rectum to reach region of perineal body
    • int anal sphincter has intrinsic supply from myenteric plexus & additional supply from both SNS (L5) and PSNS (S2-4)
  • afferent fibres from upper part of anal canal are carried by both SNS & PSNS nerves while lower anal canal sensation is via somatic sensory fibres extending to 10-15mm above dentate line (involved in continence by discriminating between fluid & faeces)
• Lymphatics
  
  • pectinate line = watershed between drainage to intra-abdominal and groin lymph nodes

** defaecation in pathophys

Question 11

Appendix

Answer 11

• blind ending tube varying in length (commonly 6-9cm) which opens into posteromedial wall of caecum 2cm below IC valve - at McBurneys point
• position of base constant in relation to caecum but may itself lie in variety of positions - retrocaecl > pelvic, subcaecal, paraileal
• mesoappendix = fold of peritoneum from left inferior layer of mesentery of TI
• ileocaecal fold/bloodless fold extends from TI to front of mesoappendix
  
  • inferior ileocaecal recess = space between fold of Treves & mesoappendix
• appendiceal artery = usu a branch of inf division of ileocolic artery which often runs behind TI to enter mesoappendix but many variations of appendicular and caecal arterial supply

Question 12

Colon

Answer 12

Asc 15, transverse 50, desc 25, sigmoid 40

Question 13

Hypogastric plexus

Answer 13

• lumbar splanchnics are derived from T12 to L2 sympathetic chain, pass down on front of aorta & are an immediate posterior relation to IMA
• these sympathetic fibres join to form the superior hypogastric plexus (sympathetic) at L5, at the level of the aortic bifurcation
• the plexus splits into 2 nerve bundles of 2-3 fibres each - the right and left hypogastric nerves which travel between the leaves of the endopelvic fascia (at the sacral promontory, 1cm lateral to the midline, 2cm medial to the ureters)
• preganglionic parasympathetic fibres from S2,3 and 4 nerves (pelvic splanchnic nerves/nervi erigentes) join the hypogastric nerves to form the inferior hypogastric plexus (mixed sympathetic and parasympathetic)
  
  • lies on side wall of pelvis on each side, superficial to endopelvic fascia & the int iliac vessels
  • in men is lateral to rectum & posterolateral to seminal vesicle, prostate and posterior part of bladder; middle of plexus is level with and just behind top of vesicle
  • in women plexus is lateral to rectum, cervix, vaginal fornix and posterolateral to bladder
  • plexus = rectangular, fenestrated plaque of nerves and ganglia ~5cm AP and 2cm vertically
  • (~half the fibres in the hypogastric nerves are myelinated (preganglionic) and they relay in the ganglia of the inf hypogastric plexus; the remaining sympathetic fibres and all the parasympathetic fibres pass through w/o relay; the parasympathetic motor and secretomotor fibres relay in the walls of viscera)
  • visc branches of inf hypogastric plexus accompany visc branches and tributries of int iliac artery and vein as neurovasc bundles
• cavernosal fibres travel from IHP in pelvic areolar tissue; form neurovasc bundles that lie immediately anterolateral and anterior to Denonvilliers’ fascia in the 10 and 2 o’clock position in relation to the rectum when viewed from above, on their way to pierce the urogenital diaphragm and enter the corpora
• pelvic parasympathetics are
  
  • motor to emptying muscle (detrusor) of bladder, and of gut from splenic flexure to rectum
  • secretomotor to gut and vasodilator to erectile tissue in perineum
• sympathetics are
  
  • motor to visceral muscle of bladder neck, int anal sphincter, vas deferens, seminal vesicles and prostatic muscle
  • also have a facilitating function in relation to uterine muscle
• sites of possible injury
  
  • high ligation of IMA
    
    • lumbar splanchnics (sympathetic) from T12-L2 sympathetic chain are direct posterior relation of IMA
    • further inferiorly superior hypogastric plexus and origin of hypogastric nerves
    • these sympathetic fibres are easily incorporated in IMA pedicle if blunt or finger dissection is used to sweep IMA off front of aorta - damage at this site can be avoided by use of sharp dissection under vision
  • at pelvic brim - posterior mobilisation of rectum
    
    • hypogastric nerves lie just beneath peritoneum and level of peritoneal reflection - identify them at pelvic brim and stay anterior and medial to them
    • NB if peritoneum is divided too far laterally before nerves have been identified higher up, they are at risk
  • lateral dissection
    
    • don’t venture out anterolaterally too far during pelvic dissection to avoid IHP
  • anterior dissection of Denonvillier’s fascia
    
    • cavernosal nerves pass anterolateral to rectum on their way to pierce urogenital diaphragm before entering corpora; they are close to posterolateral margin of prostate & lateral margins of Denonvilliers
    • dissect anterior to Denonvillier’s to level of seminal vesicles/prostate then dissect posteriorly through it to stay behind the urogenital autonomic fibres during lowest part of ant dissection
  • wide anal excision runs highest risk of damaging urogential autonomics - use intersphincteric dissection for benign disease (UC, FAP)
• sympathetic damage = ejaculatory failure or retrograde ejaculation (superior hypogastric plexus, hypogastric nerves)
• parasympathetic damage = impotence, urinary retention, vaginal dryness (inferior hypogastric plexus, anterolateral dissection deep in pelvis)

Question 14

Ischioanal fossa

Answer 14

• wedge-shaped anatomical space filled with fat lateral to anal canal
• borders:
  
  • medially and superiorly: levator ani
  • laterally and superiorly: obturator internus above, ischial tuberosity below
  • inferiorly/base: skin between ischial tuberosity and anus
  • at base
    
    • anterior boundary = posterior border of perineal body and muscles of urogenital diaphragm
    • posterior boundary = sacrotuberous ligament overlapped by lower border of glut max
  • apex = where medial and lateral walls meet (where levator ani is attached to its tendinous origin over obturator fascia)
• each fossa has an anterior recess that passes forwards above perineal membrane, potentially as far as posterior surface of body of pubis; recesses of the 2 sides don’t communicate
• posteriorly, the 2 fossae communicate w one another, low down through fibrofatty tissue of retrosphincteric sapce above anococcygeal ligament, providing horseshoe-shaped path for spread of infection from one fossa to the other
• contents
  
  • pudendal canal - in lower lateral wall of fossa, overlying obt int and medial side of isch tuberosity; contains pudendal nerve and int pudendal vessels which it conducts from lesser sciatic notch to deep perineal pouch above perineal membrane
  • inf rectal branches of pudendal nerve & int pudendal vessels run tranvsersely across ischioanal fossa from pudendal canal towards anal canal; not a straight course but arch convexely upwards through fat towards apex then downwards to anal canal so I&D of ischioanal abscesses usu dont interfere w them
    
    • accompanied by the vessels, the nerve breaks up into several branches which supply ext sphincter, mucous membrane of lower anal canal and perianal skin
  • perineal branches pass anteriorly into urogenital region

Question 15

Pelvic floor

Answer 15

Pelvic floor

Question 16

Rectum

Answer 16

• 12-15cm long, continous w sigmoid at level of S3; surgically where the sigmoid mesocolon ends and where the taeniae of sigmoid gradually broaden to form complete outer layer of longitudinal muscle (also no epiploicae in rectum)
• follows posterior concavity & has 3 lateral curves or flexures
  
  • upper and lower curves convex to right and middle curve convex to left
  • lowest part slightly dilated as rectal ampulla
• corresponding to 3 curves seen externally are transverse folds of Houston - project into lumen from concave side of these folds
  
  • the folds incorporate the circular muscle of the wall (ie not just made up of mucous membrane)
  • middle fold projects just above level at which peritoneum is reflected forwards off rectum to form floor of rectovesical or rectouterine pouch; about 8cm from anal orifice; useful landmark during sigmoidoscopy
• rectum turns downwards and backwards as anal canal 2-3cm in front of tip of coccyx
  
  • anorectal junction = slung forward by puborectalis
• connective tissue and fat around rectum = mesorectum, with mesorectal fascia (visceral fascia) surrounding it
• mesorectum = bulkier posteriorly, contains superior rectal artery and vein and branches/tributaries, lymphatics and nodes
• rel avasc plane between mesorectal fascia and parietal pelvic fascia - this is plane of surgical dissection in TME of rectum for carcinoma
  
  • plane most evident posteriorly & minimal laterally where inf hypogastric plexus lies tangentially on surface of mesorectal fascia
• peritoneum covers upper 1/3 of rectum at front and sides, middle third only at front, lower third below level of peritoneum
  
  • rectovesical/rectouterine pouch 7.5cm and 5.5cm above anal margin respectively
• anterior to rectovesical pouch = uppermost part of base of bladder & tops of seminal vesicles; below level of pouch = rest of bladder base & seminal vesicles, prostate and ends of each ureter and vas
  
  • between these structures and rectum = rectovesical fascia of Denonvilliers
    
    • connected to floor of rectovesical pouch above and to apex of prostate below
• anterior to rectouterine pouch = uppermost part of vagina (fornix+cervix); below peritoneal reflection = more of vagina w rectogenital septum intervening
  
  • this thin rectovaginal fascia fuses w perineal body below
• blood supply
  
  • principally sup rectal artery + contributions from middle & inf and median sacral vessels
    
    • lower end of IMA enters sigmoid mesocolon & changes its name to superior rectal on crossing pelvic brim
      
      • crosses left common iliac vessels medial to ureter & descends in base of medial limb of mesocolon
      • at S3 (where rectum begins) it divides into 2 branches which descend on eitehr side of the rectum and subdivide into smaller branches
      • they continue submucosally into anal canal, where they anastomose w branches of inf rectal artery
    • middle rectals present only in ~20%​
    • inf rectals can supply rectum from below to a level at least as high as peritoneal reflection from its anterior surface
• venous drainage
  
  • veins correspond to arteries but anastomose freely w one another, forming an int rectal plexus in submucosa & ext rectal plexus outside muscular wall
  • lower end of plexus = continuous w vasc cushions of anal canal
  • main route of venous drainage = sup rectal vein to IMV
  • inf rectal veins to int pudendal veins
• lymph drainage
  
  • mainly upwards - epicolic nodes on surface of rectum, pararectal nodes in mesorectum, upwards drainage via nodes along IMA to preaortic nodes
  • lymphatic drainage from lower rectum to int iliac nodes along middle rectal and inf rectal arteries, and along median sacral artery to nodes in hollow sacrum = minimal and unlikely to be a route for metastatic spread of cancer that hasn’t breached mesorectal fascia
• nerve supply
  
  • sympathetic = from inferior mesenteric plexus
  • parasympathetic supply = S2,3,4 (pelvic splanchnic nerves) via inf hypogastric plexus; they are motor to rectal muscle
  • pain fibres accompany both sympathetic and sympathetic supplies (as for bladder)
  • sensation of distension = conveyed by parasympathetic afferents
• layers of endopelvic fascia
  
  • respect of fascial layers of pelvis allows delivery of rectum and mesorectum as one lymphovascular entity
  • cylinder of mesorectum has a bilaminar plane between it and prostate/seminal vesicles anteriorly - Denonvilliers fascia
  • and sacrum and presacral vessels posteriorly - Waldeyer’s fascia
  • although fused, this embryological plane can be recreated and mesorectum thereby delivered

Question 17

Small bowel

Answer 17

• SB 3-5m from DJ flexure to IC valve; approx 2/5 jejunum and 3/5 ileum
• jejunum vs ileum
  
  • jejunum lies coiled in upper part of infracolic compartment; ileum in lower part of infracolic compartment and pelvis
  • jejunum thicker and wider-bored than ileum
  • jejunum has plicae circulares which are absent in distal ileum; can be palpated through bowel wall
  • distal ileum assoc w whitish Peyer’s patches in mucous membrane of antimesenteric border - aggregated lymphoid follicles
  • jejunum pinker bc has more blood supply
  • mesentery of ileum characterised by shorter, more dense vascular arcades, but less well seen bc of increased mesenteric fat cf jejunum (fat in mesentery reaches bowel wall in ileum but not jejunum)
• root of SB mesentery begins to left of L1 or L2 and crosses obliquely downwards and to right to overlie right SI joint
  
  • ~15cm in length and crosses D3 (usually) or D4, aorta, IVC, right ureter
    
    • relationship w D3/D4 important bc in surgical resections of duo and pancreas, root of mesentery makes dissection in the area difficult
  • SMA and SMV enter mesentery at level it crosses duo and initially run in its base; but usu pass into mesentery towards left and only the ileocolic vessels continue to run in base towards caecum
  • bc of disparity in length between SB and root of mesentery, the mesentery has to form into a series of convolutions, usu described as being like a fan
• arterial supply
  
  • whole of SB supplied by SMA
    
    • arises behind neck of panc & at this point usu gives off the inf pancreaticoduodenal artery & middle colic artery and then passes in front of duo to enter root of mesentery
    • quite high up it gives off a right colic and ileocolic branch from its right side (sometimes coming off as a single trunk)
    • main stem then passes into mesentery itself while ileocolic continues on in root of mesentery to pass towards caecum
    • on its left side in mesentery the SMA gives off ~15 intestinal branches, w 5 being proximal and large, and rest distal and small
  • in the mesentery, each intestinal branch divides into a superior and inferior branch which anastomoses w its similar fellow above and below to form a series of arcades
    
    • in prox SB usu only 1 or 2 arcades but their number increases until by about mid SB and beyond, their number may be 5 or 6
    • then number progressively falls again til TI is reached, where only one or two are found again
    • vasa rectae arise from arcade farthest from SMA and pass straight to bowel wall; are essentially end arteries - this is an important point bc the SB doesn’t have an abundant intramural plexus like the oesophagus or stomach
    • in ileum, vasa rectae shorter but form larger series of arcades; also more fat in mesentery so windows characteristic of jejunal part not seen
    • end of SMA itself supplies region of Meckel’s diverticulum if present and anastomoses w arcades and w ileocolic branch to supply TI
• venous drainage
  
  • usu follows arterial supply though veins tend to be fewer in number; this means that artery and vein don’t always lie close together and in dissection the vein should be treated separately from corresponding artery
  • drain to SMV
• lymph drainage
  
  • jejunal & ileal lymph drains to superior mesenteric nodes via mural and intermediate nodes in mesentery
• innervation
  
  • autonomic nerves reach wall of SB w its blood vessels
  • parasympathetic vagal supply augments peristaltic activity & intestinal secretion
  • many afferent fibres whose function is uncertain
  • sympathetic supply which is vasoconstrictor & normally inhibits peristalsis, is from lateral horn cells of spinal segments T9 and 10
  • pain impulses use sympathetic pathways mainly and SB pain usu felt in umbilical region of abdomen

Question 18

Thoracic aorta

Answer 18

• Commences at lower border T4 vertebra, where arch of aorta ends
• At first to left of midline, slants gradually to midline and leaves posterior mediastinum at T12 vertebra by passing behind the diaphragm between the crura (ie behind median arcuate ligament)
• Relations
  
  • Oesophagus initially lies to its right but inclines to left so it lies progressively in front of aorta and then to its left side
  • Root of left lung lies in front of aorta above and left atrium lies in front below
• Gives off:
  
  • 9 pairs of posterior intercostal arteries
  • a pair of subcostal arteries
  • bronchial arteries
  • oesophageal vessels
  • a few small pericardial and phrenic branches
• main significance of these arteries for the vascular surgeon = branches they give to spinal column
  
  • spinal cord obtains its blood supply locally from spinal arteries – ie from vertebral, deep cervical, intercostal and lumbar arteries
  • in most pts these vessels anastomose and removing segmental supply produces no untoward effects
  • but not uncommon for one of the arteries of supply to the cord to be larger than the others; this is usu a lower intercostal or upper lumbar artery, and gets called arteria radicularis magna
    
    • arises more frequently from a left-sided artery and in a small proportion of cases it provides the major supply to the cord below its level
    • if it is divided, excluded or clamped for a long period can lead to paraplegia

Question 19

Azygos system of veins

Answer 19

• thoracic wall and upper lumbar region are drained by posterior intercostal and lumbar veins into azygos system of veins
• azygos vein
  
  • usu formed by union of ascending lumbar vein w subcostal vein of right side just below diaphragm
  • goes through aortic opening of diaphragm under right crus, lateral to thoracic duct, and passes upwards lying on sides of vertebral bodies, on a plane posterior to that of the oesophagus
  • at T4 arches forwards over the hilum of right lung and ends in SVC
  • receives lower 8 posterior intercostal veins and at its convexity the superior intercostal vein of right side
  • receives bronchial veins from right lung, pericardial veins and some veins from the middle third of the oesophagus
  • the two hemiazygos veins usu join it at levels of T7 and 8 vertebrae
• hemiazygos veins
  
  • 2 veins, lie longitudinally on left side of bodies of thoracic vertebrae
  • inferior vein, hemiazygos, is formed in abdomen by union of left ascending lumbar and subcostal vein (and often communicates with left renal vein)
    
    • passess up through left crus of diaphragm and receives veins from lower oesophagus
    • lower 4/8 left posterior intercostal veins
  • superior vein, accessory hemiazygos, receives bronchial veins from left lung
    
    • they also receive the left upper 4 posterior intercostal veins
  • may communicate w each other, but characteristically drain separately from their adjoining ends behind the oesophagus into the azygos vein
• azygos and hemiazygos veins lie in front of posterior intercostal arteries from aorta

Question 20

Common iliac arteries

Answer 20

• as termination of aorta lies slightly to left of midline, right CIA slightly longer than left
• right CIA crosses formation of IVC so that it tends to overlie termination of left CIV; this sometimes causes a relative narrowing of termination of left CIV (suggested by iliofemoral thrombosis is more common on left than right)
• left CIA isn’t related to any venous structure posteriorly near its origin w left CIV lying medial, but becoming posterior
  
  • left artery is behind root of mesosigmoid and superior rectal artery
• both arteries crossed near their termination by the ureters
• CIAs have no major branches but both give small unnamed branches to muscles, peritoneum, ureters etc
  
  • divide into ext and int iliac arteries in front of SI joints

Question 21

IVC

Answer 21

• formed by confluence of right and left CIVs in front of L5 vertebra
• ascends retroperitoneally to right of aorta & passes in a groove in liver or occasionally embedded in liver substance
• perforates tendinous portion of diaphragm and pericardium to enter the inferoposterior part of the RA
• no valves in the cava distal to a somewhat vestigial valve at its entry into right atrium
• IVC crossed at its origin by right CIA (though this may more often cross left CIV)
• in its ascent, the IVC
  
  • is crossed by root of mesentery and right gonadal artery both from left above to right below
  • lies behind duo C with its contained HOP
  • lies posterior to epiploic foramen to right of caudate lobe, though caudate process lies anterior to it
  • is crossed behind by
    
    • two lowermost right lumbar arteries lower down
    • right renal artery higher up
    • small right suprarenal and inf phrenic arteries where it lies posterior to liver
  • right adrenal gland lies to its right and partly behind it as cava becomes retrohepatic
  • right sympathetic chain is overlain by IVC in its abdominal course
• IVC most directly accessible where it lies behind epiploic foramen covered only by a glistening layer of peritoneum
  
  • vertical incision to divide peritoneum over IVC, then place tape around it (this point is above renal veins and below the higher tributaries)
• to expose renal veins: kocherise duo and pancreas, and retropancreatic cava thereby exposed
• tributaries
  
  • lumbar veins
    
    • usu 4 pairs but only caudal 3rd & 4th pairs regularly drain into posterior aspect of IVC (2nd pair of lumbar drains may drain into cava at level of renal veins but, like first pair of lumbar veins, often drain into ascending lumbar or lumbar azygos vein)
    • two left veins pass behind aorta therefore at risk during mobilisation of aorta
    • two righth veins easily damaged when IVC is retracted anteriorly during lumbar sympathectomy
  • right gonadal vein (testicular, ovarian)
    
    • only on right side that gonadal veins drain into IVC just below right renal vein
    • left vein drains into left renal vein
  • renal veins
    
    • usu enter cava at angle of ~45 degrees to vertical & left vein usu higher than right by 1-2cm
  • right adrenal vein
    
    • v short, drains into posterior aspect of IVC just before it becomes retrohepatic in position
  • right inferior phrenic vein
    
    • drains undersurface of diaphragm and drains into vena cava usu above entrance of right hepatic vein
  • hepatic veins
    
    • there are several
    • lower group = small-sized veins which are variable in number, usu from 1-3 on both right and left sides, w right draining segment VIII of right side of liver and left draining segment I (caudate lobe)
      
      • in ~15% of cases a vein in a right group may be moderately large and then called an accessory right hepatic vein
      • these veins usu have a short 1-2cm extrahepatic course & can be approached for ligation by dividing peritoneal attachments of liver and retracting the appropriate lobe to right or left
      • alternatively, when liver is being removed for transplant but IVC being retained, division of lower veins can be carried out after division of upper (major) hepatic veins
        
        • there is a tributary-free plane anterior to retrohepatic cava and a finger can be gently inserted into this plane from above, below the major veins
        • liver can then be divided through main portal fissure down to finger and the sides of liver are opened out like a book
        • tributaries entering anterolateral surfaces of cava can then be dissected free and ligated
    • upper group = major veins draining the liver
      
      • left and middle hepatic veins usu join together to enter vena cava as a common trunk
      • main trunks of all the veins have a short extrahepatic course and can be dissected free after division of the peritoneal attachments of the liver
      • as the retrohepatic vena cava is usu included w the liver in a liver transplant, the variations in hepatic drainage aren’t usu of importance for this procedure
      • variations usu involve one of the segments such as VI, VII or VIII draining directly into the IVC

Question 22

Portal vein and aberrant portal vein anatomy

Answer 22

• commences behind neck of panc where SMV and splenic veins unite
• courses upwards within free edge of lesser omentum, posterior to both CBD and hepatic artery (hepatic artery anterior to it, CBD anterolateral to it)
• at porta hepatis, portal trinity enter liver surrounded by Glisson’s capsule
• portal vein branches into right and left veins; right divides into two sectional and four segmental veins, as do the arteries and bile ducts
  
  • on left however, portal vein anatomy is unique, a reflection of its role as a conduit between systemic and portal circulations in the foetus; the left portal vein has a transverse and vertical, or umbilical, segment
    
    • transition is marked by the adjoining ligamentum teres (remnant of left umbilical vein) and the end of the vertical portion is marked by ligamentum venosum (remnant of ductus venosus)
    • both portions of left portal vein are on surface of liver, rather than within its substance as the hepatic artery and bile duct are
• tributaries
  
  • on right a small vein from GB may be encountered and on left a tributary from quadrate lobe may enter close to branching of portal vein
  • in middle portion between its branching and the duo, usu doesn’t have any tributaries
  • but as vein is dissected towards duo, several tributaries may be found - cause troublesome, even catastrophic bleeding if they are damaged
    
    • superior pancreaticoduodenal vein(s) which enter right side of portal vein behind or immediately above the duo
    • right and sometimes left gastric veins also enter portal system somewhat variably; if they join the portal vein they do so on its left side usu behind duo but occasionally higher, where they will be in field of dissection
• variations of portal vein (not v common)
  
  • most common variation = trifurcation - division into left, right anterior and right posterior branches
  • other variations include right anterior or posterior arising from portal vein early, or off the left portal vein

Question 23

Lymphatic system

Answer 23

• abdominal lymphatics
  
  • lymph drains along coeliac, SMA and IMA to preaortic nodes situated around origin of these vessels
  • similarly lymphatics pass back along paired branches of aorta, both visceral and somatic, to para-aortic nodes which lie alongside aorta
• cisterna chyli
  
  • from highest of aortic groups a variable number of intestinal and lumbar lymph trunks join to form the elongated sac-like Cisterna Chyli
  • situated under cover of right crus
  • in front of bodies of L1 and L2
  • between aorta and azygos vein
  • becomes continuous w thoracic duct
• thoracic duct
  
  • commences at T12 at upper end of cisterna chyli, between aorta and azygos vein
  • passes upwards to right of aorta & comes to lie against right side of oesophagus
  • inclining to left, alongside aorta, passes behind oesophagus at T5 to reach left at superior mediastinum; lies to left of oesophagus on a posterior plane
  • lies anterior to right aortic intercostal arteries & terminal parts of hemiazygos and accessory hemiazygos veins
  • in superior mediastinum lies posterior to arch of aorta & left subclavian artery
  • at root of neck at ~level of inf thyroid artery/3cm above clavicle, arches forward and to the left, behind carotid sheath and its contents, but in front of the sympathetic trunk, vertebral artery and vein and thyrocervical trunk; may even pass in front of scalenus anterior before passing back downwards and ending variably in confluence of subclavian and IJ veins
  • in neck receives left jugular and subclavian lymph trunks
  • drains all of body except right arm and right side of head, neck and thorax which is drained by right lymphatic system
    
    • posterior right thoracic wall enters right lymphatic duct
      
      • much smaller than thoracic duct; drains right intercostal nodes and right bronchomediastinal trunk
      • may receive right jugular and subclavian lymph trunks before it opens into commencement of right brachiocephalic vein, or they may remain separate and open independently into jugulosubclavian junction
    • right upper limb drains into right subclavian trunk
    • right side of H&N drains into right jugular lymph trunk
  • ok to ligate if damaged at time of oesophagectomy

Question 24

Thoracic duct & cisterna chyli

Answer 24

• abdominal lymph drains along coeliac, SMA & IMA to preaortic nodes around origin of these vessels
• similarly lymphatics pass back along paired branches of aorta, both visceral and somatic, to para-aortic nodes alongside aorta
• cisterna chyli
  
  • from highest of aortic groups a variable number of intestinal & lumbar lymph trunks join to form the elongated sac-like cisterna chyli
  • under cover of right crus
  • in front of bodies of L1 & L2
  • between aorta & azygos vein
  • becomes continuous w thoracic duct
• thoracic duct
  
  • commences at T12 at upper end of cisterna chyli, between aorta & azygos vein
  • passes upwards to right of aorta & comes to lie against right side of oesophagus
  • inclining to left, alongside aorta, passes behind oesophagus at T5 to reach left at superior mediastinum; lies to left of oesophagus on a posterior plane
  • lies anterior to right aortic intercostal arteries & terminal parts of hemiazygos and accessory hemiazygos vein
  • in superior mediasitnum lies posterior to arch of aorta and left subclavian artery
  • at root of neck at about level of inf thyroidal artery/3cm above the clavicle, arches forwards and to the left, behind carotid sheath and its contents, but in front of sympathetic trunk, vertebral artery and vein and thyrocervical trunk; may even pass in front of scalenus anterior before passing back downwards and ending variably in confluence of subclavian and IJ veins
  • in neck receives left jugular and subclavian lymph
  • drains all of body except right arm and right side of head, neck and thorax which is drained by right lymphatic system
  • fine to ligate at oeosphagectomy bc of numerous alternative lymphatic pathways
• ​right thoracic system
  
  • posterior right thoracic wall enters right lymphatic duct
    
    • much smaller than thoracic duct, drains right intercostal nodes and right bronchomediastinal trunk
    • may receive right jugular and subclavian lymph trunks before it opens into commencement of right brachiocephalic vein, or they may remain separate and open independently into jugulosubclavian junction
  • right upper limb drains into right subclavian trunk
  • right side of H&N drains into right jugular lymph trunk

Question 25

Sympathetic trunk

Answer 25

• preganglionic sympathetic cell bodes are in the lateral horn cells of all the thoracic and upper two lumbar segments of the spinal cord (thoracolumbar part of the autonomic nervous system)
• these leave via the anterior nerve root (w axons of the anterior horn cells) to reach the spinal nerve and its anterior ramus
• the connecting links from here to the sympathetic trunk and its ganglia are the rami communicantes
  
  • normally two rami; white ramus communicans is the more distal of the two, and is the one containing the preganglionic fibres (which are myelinated, hence called white); the greay remus comunicans contains efferent postganglionic fibres (which are unmyelinated, hence grey)
  • every spinal nerve receives a grey ramus, containing postganglionic sympathetic fibres which ‘hitch-hike’ along the nerves and accomapny all their branches; they leave the spinal nerve only at the site of their destination
    
    • mainly vasoconstrictor in function, though some go to sweat glands in skin and to arrectores pilorum muscles of hair roots - chiefly for function of temp regulation
  • all the thoracic and upper two lumbar nerves have both white and grey rami connecting them to sympathetic ganglia; the cervical, lower lumbar and sacral nerves don’t have white adn the ganglia they are connectied with receive preganglionic fibres from the thoracolumbar outflow through the chain
• sympathetic trunk extends alongside vertebral column from base of skull to coccyx
• theoretically there is a ganglion for each spinal nerve but fusion occurs, espsec in cervical region where
  
  • upper four unite to form the superior cervical ganglion
  • fifth and sixth form the middle cervical ganglion
  • seventh and eighth form inferior cervical ganglion (and often w first thoracic ganglion as well to form the cervicothoracic or stelltae ganglion)
• elsewhere there is usu one ganglion less than the number of nerves: 11 thoracic, 4 lumbar and 4 sacral
• having reached a sympathetic trunk ganglion, the incoming preganglionic fibres have one of three possible synaptic alternatives
  
  • most common = synapse w cell bodies in a trunk ganglion, either in the one they entered or to run up or down the trunk to some other trunk ganglion
  • second alternative = to leave trunk ganglion w/o synapsing and to pass in a ganglion in an autonomic plexus for synapse
  • third option (applies only to small no of fibres) = leave trunk (w/o synapsing) to pass to suprarenal gland, where certain cells of medulla can be regarded as modified ganglion cells
• because there is no sympathetic outflow from cervical, lumbar or sacral parts of cord, preganglionic fibres which are destined to synapse w cell bodies whose fibres are going to run w cervical nerves must ascend in sympathetic trunk to cervical ganglia, and those for lower lumbar and sacral nerves must descend in the trunk to lower lumbar and sacral ganglia
• each sympathetic trunk ganglion has a collateral or visceral branch, usu called a splanchnic nerve in the thoracic, lumbar and sacral regions, but in the cervical region called a cardiac branch bc it proceeds to the cardiac plexus
  
  • visceral branches generally arise high up and descend steeply to form plexuses for the viscera
  • thus cardiac branches arise from the three cervical ganglia to descend into the mediastinum to the cardiac plexus, which is supplemented by fibres from the upper thoracic ganglia
  • from fifth and lower thoracic ganglia, three splanchnic nerves plierce the diaphragm to reach the coeliac plexus and other pre-aortic plexuses, which are also joined by lumbar splanchnic nerves from the upper lumbar ganglia
  • fibres from these plexuses, and splanchnic nerves from the lower lumbar ganglia, descend to the superior hypogastric plexus and thence to the right and left inferior hypogastric plexuses
• the sympathetic visceral plexuses thus formed are joined by parasympathetic nerves: vagus to the coeliac plexus and pelvic splanchnics (S2-4) to the inferior hypogastric plexuses
  
  • the mixed visceral plexuses reach the viscera by direct branches and by branches that hitch-hike along the relevant arteries
• in addition to visceral branches, all trunk ganglia also give off vascular branches to adjacent large blood vessels
  
  • cervical ganglia give branches to carotid and vertebral arteries
  • thoracic and lumbar ganglia give filaments to the various aortic plexuses adn from there to aortic branches incl common iliac arteries, continued along the internal and external iliac arteries as far as the proximal part of the femoral artery
• many afferent fibres hitch-hike along sympathetic efferent pathways
  
  • some form the afferent limb for unconscious reflex activities; others are concerned w visceral pain
  • all have their cell bodies in the posterior root ganglia of spinal nerves (not in sympathetic ganglia) at approx the same segmental level as the preganglionic cells
  • afferent fibres reach spinal nerve via white ramus communicans then join posterior root ganglion, from which central processes enter spinal cord by posterior nerve root
• thoracic part of sympathetic trunk lies posterior to costovertebral pleura and is hence not a content of the posterior mediastinum
• contains about 12 ganglia, most of which lie anterior to the heads of ribs
• first thoracic ganglion often fused w infeiror cervicl gangion (stellate ganglion), and lies anterior ot neck of first rib
• lowest three ganglia lie lateral to the corresponding vertebral bodies
• postganglionic sympahteitc fibres pass to cardiac and pulmonary plexuses, trachea, oesophagus, thoracic aorta and its branches
• splanchnic nerves, three in number, come from lower eight ganglia and consist mainly of preganglionic fibres
  
  • lowest (least splanchnic nerve) leaves twelfth ganglion
  • lesser splanchnic nerve from tenth and eleventh
  • greater splanchnic nerve from fifrth to ninth ganglia
  • each pierces crus of its own side
• thoracic trunk continues downwards into abdomen by passing behind the medial arcuate ligament of diaphragm on front of psoas major
• coeliac plexus lies around origin of coeliac trunk above upper border of pancreas
  
  • greater and lesser splanchnic nerves pierce crura of diaphragm and enter the two large coeliac ganglia which lie in front of the crura, the right one behind the IVC and the left behind the splenic artery
  • the splanchnic nerves are almost all preganglionic and many relay in the coeliac ganglia
  • the least splanchnic nerve relays in a small renal ganglion behind the renal artery; this is merely an offshoot of the main coeliac ganglion itself
  • separated masses of ganglion may lie on the aorta at the superior and even the inferior mesenteric artery origins
• postganglionic fibres from the coeliac ganglia and preganglionic splanchnic fibres form a network on the aorta, the relevant parts of which are the coeliac, superior mesenteric, intermesenteric (abdominal aortic) and inferior mesenteric plexuses, in accordance w their relation to the origin of the midline gut arteries
  
  • the fibres from these plexuses supply all the abdominal viscera, which they reach by streaming along the visceral branches of the aorta
  • those passing to the kidney pick up the branches of the renal ganglion to form the renal plexus behind the renal artery
  • testis and ovary are supplied by a sympathetic plexus that accompanies each gonadal artery
  • the sympathetic fibres are vasomotor, motor to sphincters (eg pyloric), inhibitory to peristalsis and carry sensory fibres from all the viscera supplied
• preganglionic fibres from the greater splanchnic nerve pass w/o relay to the cells of the suprarenal medulla (these cells share a common origin from neural crest ectoderm w the cell bodies of sympathetic ganglia) - cause release of adrenaline
  
  • vasomotor supply to suprarenal gland reaches it by postganglionic fibres which have relayed in coeliac ganglion
• lumbar part of thoracic trunk runs down behind peritoneum on vertebral bodies along medial margin of psoas
• as elsewhere it lies in front of the segmental vessels, the lumbar arteries and veins
• left lumbar trunk lies beside the left margin of the aorta, with para-aortic lymph nodes in front of it, which the right trunk lies behind the IVC
• usually 4 lumbar ganglia, with white rami communicantes from the first two lumbar nerves joining the trunk
• grey rami communicantes from the lumbar ganglia accompany the lumbar arteries around the sides of the vertebral bodies, medial to the fibrous arches, to join the anteiror rami of lumbar nerves, for distribution to the body wall and lower limb, through branches of the lumbar plexus
• lumbar splanchnic nerves arise from all lumbar ganglia
  
  • those from first and second ganglia pass to plexuses in front of the aorta; those from third and fourth ganglia pass respectively in front of and behind the CIAs
  • they join with each other and with fibres from the aortic plexuses to form the superior hypogastric plexus, which comprises both pre- and postganglionic sympathetic fibres
  • this plexus lies anterior to the aortic bifurcation adn the left common iliac vein and between the common iliac arteries, in front of L5 vertebra and the sacral promontory; lies behind the parietal peritoneum
  • divides into right and left hypogastric nerves

Question 26

Lumbosacral plexus

Answer 26

Lumbosacral plexus

Question 27

Adrenals

Answer 27

Overview

• Retroperitoneal structures
• 4-7g; 2-6mm thick; 2-4cm length
• golden colour secondary to cholesterol in cortex
• Each adrenal enveloped by its proper capsule in addition to sharing Gerota’s fascia with the kidneys
• RIGHT = pyramidal
• LEFT = crescentic

Structure

• MEDULLA = 15% volume of adrenal
  
  • consists of vascular spaces & eosinophilic phaeochromocytes of variable size containing polymorphic nuclei
  • Phaeochromocytes = characterized histologically by their uptake of dichromate salts & hence referred to as chromaffin cells
• CORTEX = 85% volume of adrenal
  
  • 3 layers (outside to in = GFR, salt, sugar sex)
  • zona glomerulosa – produces mineralocorticoids
    
    • columnar cells w v little cytoplasm cf nuclei, organized into clusters
  • zona fasciculata – largest cortical zone (75% cortex) – produces glucocorticoids > sex steroids
    
    • poorly staining, polyhedral cells organized in radial columns
  • zona reticularis – produces sex hormones, espec DHEAS > cortisol
    
    • rounded branching cords of cells

Relationships

• RIGHT lies at upper pole right kidney, between right crus and IVC
  
  • Lies on diaphragm & encroaches onto right kidney
  • Abuts posterolateral surface of retrohepatic IVC (ie anterior surface overlapped medially by IVC)
  • Rest of anterior surface in contact above with bare area of liver, & covered below by peritoneum of posterior wall of hepatorenal pouch
  • Right adrenal fossa bounded by right kidney inferolaterally, diaphragm posteriorly & bare area of liver anterosuperiorly
• LEFT drapes over upper medial side left kidney with tail of panc anterior & left diaphragm crus posteriorly
  
  • Lies on left crus and overlaps front of left kidney
  • Lies between left kidney & aorta, with its inferior limb extending further caudad towards renal hilum than right side
  • Upper part of ant surface covered by peritoneum of posterior wall of lesser sac forming part of stomach bed: lower part in contact with panc & splenic vessels

Blood supply

• From 3 distinct vessels
  
  • Superior adrenal arteries – from inferior phrenic arteries
  • Middle adrenal arteries – from juxtaceliac aorta
  • Inferior adrenal arteries – from renal arteries
    
    • Inferior most prominent & commonly a single identifiable vessel

Venous drainage

• Single adrenal vein – drains into IVC on right & renal vein on left
• Right vein short as it is wide (0.5cm) – more difficult to operate
  
  • In >85%, single vein into IVC; in others can have adrenal-IVC-renal vein confluence OR adrenal-renal vein confluence OR high single vein into IVC OR adrenal-IVC-right hepatic vein trifurcation OR adrenal-hepatic vein confluence
• Left vein = 2cm
• Veins drain from medulla therefore venous return from cortex flows through medulla – relevant as glucocorticoid hormones secreted by cortex activate phenylethanalomine N-methyltransferase (PNMT) – an enzyme involved in synthesis of catecholamines
  
  • PNMT is only present in the adrenal medulla and converts noradrenaline to adrenaline; so extra-adrenal phaeos (paragangliomas) don’t produce adrenaline

Lymphatic drainage

• Medullary and subcapsular lympatic plexuses –> lymphatics that follow arterial supply to para-aortic lymph nodes

Innervation

• Adrenal cortex receives a few vasomotor fibres – but otherwise isn’t neural; is activated by ACTH from anterior pituitary, or angiotensin II in the case of aldosterone
• Medulla richly supplied w fibres derived from splanchnic nerves (T5-9)
  
  • Myelinated preganglionic sympathetic fibres from splanchnic nerves via coeliac plexus; fibres synapse directly w medullary cells/phaeochromocytes/chromaffin cells, filled with granules containing catecholamines
• blood vessels receive usual postganglionic sympathetic supply

Question 28

Duodenum

Answer 28

Overview and relations

• A C-shaped tube of GI tract lying in front and to the right of the IVC and aorta
• First 2.5cm are contained between peritoneum of lesser and greater omenta, but remainder is retroperitoneal
• Has 4 parts – superior, descending, horizontal and ascending
• Makes its C-shaped loop around head of pancreas, which is opposite body of L2, so first part may be said to lie at level of L1, second on right side of L2, third crosses in front of L3 and fourth is on level of L2 vertebrae

First part

• 2 inches in length
• runs to right, upwards and backwards from pylorus
• first 2.5cm (duodenal cap) lies between peritoneal folds of greater and lesser omenta
• superiorly: forms lowermost boundary of opening into lesser sac
• inferiorly: head of pancreas
• posteriorly:
  
  • to first 2.5cm: GDA, bile duct, portal vein; behind these structures lie IVC
  • to next 2.5cm: extends to medial aspect right kidney, posterior surface bare of peritoneum
• anteriorly:
  
  • GB anterior to duodenal cap
  • Inferior surface of right lobe of liver

Second part

• 3 inches in length
• halfway along receives: common opening of bile duct and main pancreatic duct at hepatopancreatic ampulla (of Vater) which opens on summit of major duodenal papilla, 2cm from pylorus; 2cm proximal = small opening of accessory pancreatic duct (on minor duo papilla)
• posteriorly: curves downward over hilum of right kidney
• anteriorly: covered with peritoneum and crossed by attachment of transverse mesocolon
  
  • so upper half lies in supracolic compartment to left of hepatorenal pouch (in contact w liver) and lower half lies in right infracolic compartment medial to inferior pole of right kidney (in contact with coils of jejunum)
• laterally:
  
  • to upper half – hepatorenal pouch (in contact w liver)
  • to lower half – inferior pole of right kidney (in contact with coils of jejunum)
• medially: lies alongside head of pancreas, approx. at level of L2

Third part

• 4 inches in length and curves forwards from right paravertebral gutter over slope of right psoas muscle and passes over IVC and aorta to reach left psoas
  
  • occupies the space on the anterior aorta between the origins of the SMA and IMA; may be compressed here by an acute SMA angle
• Posteriorly: right psoas with gonadals and ureter intervening, left psoas
• Superiorly:
  
  • Superiorly/anteriorly: superior mesenteric vessels
• Anteriorly:
  
  • superior mesenteric vessels
  • leaves of commencement of mesentery of SB, sloping down from DJ flexure –therefore lies in both right (mainly) and left infracolic compartments
  • coils of jejunum
• Inferiorly: commencement of IMA

Fourth part

• 1 inch in length and ascends to left of aorta, lying on left psoas muscle and left lumbar sympathetic trunk, to reach lower border of body of panc and re-enter the peritoneal cavity at the DJ flexure
• Breaks free from the peritoneum that has plastered it down to the posterior abdominal wall and curves forwards and to right as DJ flexure
  
  • This pulls up a double sheet of peritoneum from the posterior abdominal wall, the mesentery of the SB, which slopes down to right across third part of duo and posterior abdominal wall
• Anteriorly: peritoneal floor of left infracolic compartment and coils of jejunum
• Posteriorly: left psoas muscle, left lumbar sympathetic trunk
• To right side: head of pancreas
• Superiorly: body of pancreas
• To left side of DJ flexure: IMV

DJ flexure and paraduodenal recesses

• DJ flexure fixed to left psoas fascia by fibrous tissue & may be further supported by suspensory muscle of duo (muscle or ligament of Treitz)
  
  • This is a thin band of connective tissue which may contain muscle – skeletal muscle fibres that run from right crus of diaphragm to connective tissue around coeliac trunk and smooth muscle fibres that run from there, behind the pancreas & in front of left renal vein, to muscle coat of the flexure
• To left of DJ flexure certain peritoneal folds may cover recesses or fossae
  
  • Paraduodenal recess proper lies behind a fold raised by upper end of IMV; an incarcerated internal hernia in this fossa may obstruct and thrombose the vein, and there is danger of dividing the vein if the peritoneum has to be divided at operation to free the hernia
  • Horizontal folds of peritoneum may cover superior and inferior duodenal recesses
  • Retroduodenal recess may be found behind flexure
  • Mouths of these four recesses/fossae face each other

Structure

• Most of mucous membrane of duo, like rest of SB, is thrown into numerous circular folds (plicae circulares or valvulae coniventes); but walls of first 2.5cm are smooth

Arterial supply

• the foregut-midgut transition is at the site of the ampulla of Vater; the duodenum therefore receives blood supply from both the coeliac axis and the SMA
• first 2cm, the usual site of ulceration, receives blood from the hepatic, GDA, supraduodenal, right gastric and right gastroepiploic arteries
• also supplied by the superior pancreaticoduodenal arteries (from GDA) and inferior pancreaticoduodenal arteries (from SMA)

Venous drainage

• To tributaries of superior mesenteric and portal veins

Lymphatic drainage

• Is to both the coeliac axis and SMA nodal basins

Innervation

Question 29

GB

Answer 29

Overview – size, shape, position

• pear-shaped sac, storage capacity 30-50mL
• 3 parts:
  
  • fundus: rounded, end portion of gallbladder; which projects below inferior surface of liver
    
    • surface marking tip of 9^th costal cartilage where transpyloric plane crosses right costal margin at lateral edge of right rectus sheath
  • body: largest part of the gallbladder; occasionally in contact w transverse colon and prox duo
  • neck: GB tapers to become continuous w cystic duct, leading to biliary tree.
  • Hartmann’s pouch = expansion of prox extent of GB = prob pathological occurrence related to stones
• Sits on cystic plate at junction of left and right lobes of liver, onto segment V to right of quadrate lobe, which itself is bound by cystic plate on right and falciform to left

Structure

• Fibromuscular sac w surprisingly small amount of smooth (striated) muscle in its wall
  
  • Muscle arranged in circular, oblique and longitudinal fashion
• Mucous membrane = lax areolar tissue lined w single layer simple cuboidal epithelium
• Projected into folds which produce honeycomb appearance in body but arranged in spiral manner in neck & cystic duct (‘spiral valve’ of Heister)
• Epithelial cells actively absorb water & solutes from bile & concentrate it
• Mucus secreted by columnar epithelium but no goblet cells, & mucus-secreting glands are present only in the neck

Relationships

• Surrounded by peritoneum, binding it to visceral covering of liver
• Close to
  
  • Anteriorly & superiorly: inf border of liver & ant abdo wall
  • Posteriorly: transverse colon & prox duodenum
  • Inferiorly: biliary tree and duo

Cystic and hilar plates

• Hilar plate is located in hilum of liver
  
  • Bounded:
    
    • Above by inf part of segment IV
    • On right by Rouviere’s sulcus: a landmark demarcating division between segment V and segment VI; contains branches of the right posterior sectional pedicle in 70%
    • On left?? By cystic plate & is continuous with umbilical plate
  • Upper border is curved & lies superior to right and left hepatic ducts; it is this taught, firm, upper curved edge of the hilar plate that is dissected free from undersurface of liver – specifically the quadrate lobe/lower most part of segment IV – when one is ‘lowering’ the hilar plate to expose the left hepatic duct, the biliary ductal confluence & the right hepatic duct when repairing a biliary stricture
  • The hilar plate can be detached from quadrate lobe bc no branch originate from left vessels along anterior margin or upper surface of hilar plate
  • Small caudate branches originate from along the posterior margin of hilar plate
• Anterior Glisson’s sheath generally runs behind junction between cystic plate and hilar plate, and the posterior-inferior Glisson’s sheath runs behind Rouviere sulcus
  
  • As a result, the bile ducts & blood vessels of right side can be dissected easily w/o widely opening the hilar plate
• The cystic plate is located in GB bed & is continuous w capsule of segment V, segment IVb and Glisson’s sheath of anterior segment of liver
  
  • Continued dissection in this plane behind cystic plate will eventually reach right portal pedicle & if sheath of pedicle is breached, there is a v high risk of injury to right hepatic artery & right portal vein

Cystic duct

• 2-8cm long but apparent length at operation 2-4cm (bc cystic duct enters CHD under layer of soft tissue surrounding porta)
• entry into CHD also variable and may be:
  
  • angular 70%, parallel 20%, spiral 10% (can be ant or post)
• can also have v short cystic duct, long cystic duct and if parallel can be v close together; can also have accessory cystic duct
• 1-2% may join the RHD or RPSD
• may also cross anomalous low lying RHD in 1/1000 cases – injury to these aberrant ducts can occur b/c appear to be in continuity w cystic duct itself
• neck of GB and cystic duct contain spiral folds of mucosa – spiral valve

Arterial supply

• cystic artery
  
  • arises from right hepatic artery on right side of RHD in Calot’s triangle and passes lat to GB in 70% of cases
    
    • usu divides into ant & post branches, latter running a course between GB & liver
  • in 25% of cases arises to left of duct system & usu crosses in front of ducts to reach GB
  • cystic artery can be v short w RHA in close proximity or even adherent to cystic duct or Hartman’s pouch
  • in 2-3% artery divides early into multiple small branches & signif cystic artery never discovered
• aberrant anatomy
  
  • 20% arises from CHA, its bifurcation or from L hepatic artery
  • 10% arises from accessory RHA
  • 2.5% arises from GDA
  • also SMA

Venous return

• by multiple small veins in GB bed into substance of liver & so into hepatic veins
• 1 or more cystic veins may be present but uncommon; run from neck of GB into right branch of portal vein
  
  • the one which occasionally causes annoying bleeding (espec during cannulation for IOC) runs w the cystic duct, often on its superior aspect

Lymphatic drainage

• usu prominent LN overlying ant branch of cystic artery near its insertion into GB – cystic/Calot’s node
• nodes in porta hepatis
• and a node at anterior boundary of the epiploic foramen
• from here lymph passes to coeliac group of preaortic nodes
• 2 chains of LNs along portal vein
  
  • first chain between CBD & portal vein and most of external surface of GB drains (via Calot’s node) into the chain -> joins with pancreaticoduodenal nodes & drains to aortic nodes
  • second chain between portal vein & hepatic artery; receives lymph from hepatic surface of GB -> coeliac nodes
  • so lymphadenectomy for GB ca should skeletonize BD, hepatic vessels, PV)
  • in ~10% lymphatic channels from ext surface GB traverse segment V of liver -> PV-BD chain
  • in another 10% the int surface has lymphatic channels which traverse segment IV -> PV-HA chain – so some recommend removal of segs IV & V of liver w GB ca

Innervation

• at cholecystectomy, GB is grasped and pushed cephalad and laterally to elevate the entire right hemiliver, thus exposing GB and porta hepatis
• a large branch of middle hepatic vein lies close to liver surface in GB bed ~8% of cases
• cystic duct best dissected and clipped close to its entry into the GB in order to avoid any of the variations of ductal, arterial or venous anatomy here
• most common cause for major bile duct injury = mistaking CBD for cystic duct
  
  • usually due either to significant adhesions tethering infundibulum to side of CHD or due to improper traction placed on GB – directly cephalad, aligning cystic and common bile ducts, rather than pulling GB lateral to accentuate the angle between cystic and common bile ducts

Question 30

Lesser sac

Answer 30

Overview

• A sub-section of the peritoneal cavity behind the stomach
• Opens into the greater sac through a slit-like aperture, the Foramen of Winslow, defined by the following boundaries:
  
  • Posteriorly, the IVC
  • Anteriorly, the free edge of the hepatoduodenal ligament with the portal triad within
  • Superiorly, the caudate lobe
  • Inferiorly, the pylorus and duodenum

Boundaries

• Anterior surface:
  
  • Posterior layer of lesser omentum
  • Peritoneum of posterior stomach
  • Posterior of the two anterior layers (fused) of the greater omentum
• Posterior surface:
  
  • Anterior of the two posterior layers of the greater omentum which adheres to, but is surgically separable from, the anterior surface of the transverse colon and the transcerse mesocolon
  • above the attachment of the transverse mesocolon to the anterior border of the pancreas, the posterior wall is formed by the peritoneum that covers the
    
    • front of the neck and body of pancreas
    • upper part of left kidney
    • left suprarenal gland
    • commencement of abdominal aorta
    • coeliac artery (plexus and nodes)
    • part of the diaphragm
• theoretically the cavity of the lesser sac should extend down between the anteiror two layers and teh posteiror two layers of the greater omentum, but because of fusion of these layers the cavity doesn’t extend much below the transverse colon
• the narrow upper border of the lesser sac is at the right side of the abdominal oesohpagus, where the peritoneum of the posteiror wall is reflected anteriorly on the inferior aspect of the diaphragm to form the posteiror layer of the lesser omentum
• at the tail end of teh pancreas the left border of teh lesser sac is formed by splenorenal and gastrosplenic ligaments

Question 31

Liver

Answer 31

• overview
  
  • 1500g, 1500mL blood/min
  • Surface marking:
    
    • upper margin ~level with xiphi, arching slightly up on each side. On left reaches 5th ICS, 7-8cm from midline. On right reaches 5th rib, curving down to right border which extends from ribs 7-11 in MAL
    • inf border = along a line joining R lower and upper L extremities; lies approx level w R costal margin, while centrally crosses behind upper abdo wall between costal margins ~handsbreadth below xiphisternal joint
  • encased by thin fibrous capsule, Glisson’s capsule - covers entire organ except for large bare area posteriorly where liver in contact w IVC & diaphragm
• surfaces
  
  • diaphragmatic
    
    • subdivided into anterior, superior, posterior, right surfaces which merge into one another w/o clear demarcations
    • covered w peritoneum except bare area which contains IVC & hepatic veins
      
      • bare area in contact w diaphragm & right suprarenal gland
  • visceral
    
    • related to stomach, duo, hepatic flexure
    • most main vessels & ducts enter or leave at porta hepatis which is on viceral surface (but hepatic veins emerge from posterior surface)
  • NB sharp inferior border separates right & ant surfaces from visceral surface which slopes upwards & backwards from here to merge w posterior surface
• lobes
  
  • morphologically, 4 lobes
    
    • falciform divides into left and right on diaphragmatic surface & ligamentum venosum & teres provide demarcation on visceral surface
    • quadrate lobe (IVb) demarcated on visceral surface by GB fossa, porta hepatis and ligamentum teres
    • caudate lobe (I) demarcated by IVC groove, porta hepatis and ligamentum venosum/lesser omentum
  • functionally, divided by Cantlie’s line (middle hepatic vein lies in this plane)
    
    • vertical plane that divides liver into left and right lobes extending from IVC posteriorly to middle of GB fossa anteirorly
• ligaments/peritoneal attachments
  
  • falciform ligament
    
    • vestigial of ventral mesogastrium
    • attaches front of liver to anterior abdominal wall, descending to attach to umbilicus
    • at superior surface of liver a reduplication of left leaf forms left triangular ligament; right leaf passes to right, in front of IVC & becomes upper layer of coronary ligament
  • ligamentum teres
    
    • obliterated umbilical vein which used to join left branch of portal vein (supposedly but in reality its lumen is usu closed rather than obliterated & can be dissected at the umbilicus, dilated and used for access to left portal vein in >50% pts; also channel occasionally opens up in portal HTN, forming a collateral channel to bypass liver and in these circumstances the umbilical vein can often reach quite large proportions)
    • lies within free edge of falciform
    • acts as a guide to ductal system of segment III as it passes into a fissure which separates segment III from segment IV of right lobe (quadrate)
      
      • can be traced through to point of entry into left portal vein where it tends to fan out somewhat; the biliary duct from segment III usu joins left hepatic bile duct behind and somewhat superior to this junction
    • has small paraumbilical veins extending from portal system to umbilicus travelling within ligamentum teres; these should be ligated before being divided to prepvent bleeding from these veins
    • triangle formed by posterior part of falciform ligament has common trunk of middle and left hepatic vein lying at base on left and a depression of liver tissue in front of the vena cava on right; this depression lies between left and right hepatic veins
  • ligamentum venosum
    
    • cord formed by obliteration of ductus venosus
    • separates left lobe from caudate
  • coronary and triangular ligaments
    
    • attach posterior surface of liver to diaphragm
    • coronary ligament lays to right, consisting of a superior and inferior layer
      
      • where they meet forms right triangular ligament
      • inferior leaf then passes back and runs behind (?over) IVC, eventually to take part in formation of lesser omentum
      • the two leaves of the coronary ligament are widely separated & posterior surface of liver here lies against diaphragm w/o any peritoneal covering - bare area of liver
    • leaves of coronary ligament passing to left come into proximity almost immediately & form left triangular ligament - suspends posterosuperior surface of left side of liver to diaphragm
      
      • IVC and entering hepatic veins lie within bare area of liver
      • necessary to divide these ligaments in order to gain mobility of liver for resections; should be appreciated that as division reaches towards midline, important venous structures are in close proximity & therefore are at risk
• fissures
  
  • importance = they mark the boundaries of portal units of the liver (help in removing anatomically defined portions of liver), and main hepatic ceins run in main fissures
  • main/middle fissure divides right and left functional sides, separating segment IV from V and VIII
    
    • on anterior and superior surface of liver its plane is in a line which joins tip of GB bed back to ~midpoint of IVC
    • on inferior surface, line runs down middle of GB bed across caudate process then up along the middle of IVC
    • main trunk of middle hepatic vein lies in this plane
  • left fissure/left intersectional plane - separates left lateral sector from medial sector
    
    • can be marked approx on liver surface by joining 2 points
      
      • first point = midway along ant edge of liver between falciform ligament and left extremity
      • second point = at left side of base of triangular insertion of falciform ligament in front of IVC
    • plane of fissure = approx midway between horizontal and vertical in its obliquity back to IVC
    • (attachment of falciform & grooves for ligamentum teres & ligamentum venosum)
    • main trunk of left hepatic vein in this plane
  • right fissure/right intersectional plane
    
    • no external markings - runs in oblique direction posteriorly & medially from middle of front of right lobe towards vena caval groove
    • plane tends more to coronal than anything else but v variable in its anterior extent - may lie much closer to right margin of GB bed (40%) or extend out to right anteiror extremity of liver (10%)
    • corresponds w right hepatic vein
  • umbilical fissure
    
    • marked morphologically on inferior liver surface at point where falciform ligament reaches anterior border of liver
    • on superior surface, fissure lies deep to line of attachment of falciform ligament
    • separates III from IV
    • often a vein of some surgical importance in this fissure - best called vein of umbilical fissure to avoid confusion it w umblical vein running w round ligament
  • fissure venosum = continuation of umbilical fissure on posterior surface of liver
    
    • lesser omentum passes into this fissure
    • was the ductus venosus in fetal life which connected the left branch of portal vein to left hepatic vein - bypass system
    • caudate process lies behind this fissure separated from it only by lesser omentum
    • fissrue lies more or less in a coronal plane and continuation of this plane leads to plane of dorsal fissure
  • dorsal fissure separates segment IV from I
    
    • prob least definable of all the fissures
    • in same plane as fissure venosum, so that when surgeon places fingers in fissure they point to the division between segment I behind and segment IV in front
• segments/sections
  
  • Couinaud
  • on basis of blood supply & biliary drainage (the intrahepatic distribution of the portal trinity) there are 4 main hepatic sectors/sections, furhter subdivided into 8 segments
    
    • right posterior (lateral) section = segments VI and VII
    • right anterior (medial) section = segments V and VIII
    • left medial section = segments IVa, IVb, I
    • left lateral section = segments II and III
    • segments are numbered beginning at inf part of liver & going around portal vein in an anticlockwise direction (when viewed from below)
    • bc plane between right medial and lateral sectors is coronal, it means the segmetns of right medial sector tend to lie in front of segments of right lateral sector, so when viewed from in front, segment VI tends to lie behind segment V
    • also means posteiror surface of right side is made up mainly of segments VII and VI
  • hepatic veins lie in intersectional planes
  • portal vein runs between ‘upper and lower’ segments, sending branches to upper and lower segments
  • the caudate lobe, despite lying to left of plane between the two functional lobes of the liver, is an autonomous segments receiving blood from right and left branches of hepatic artery and portal vein, draining bile into right and left hepatic ducts & having independent venous drainage into IVC (its separateness from right and left livers is demonstrated in hepatic venous occlusion where liver is congested and functioning poorly - caudate lobe hypertrophies perhaps also taking some of hepatic venous drainage back to IVC
    
    • bound by IVC to its right and continuation of umbilical fissure (fissure for ligamentum venosum) on its left
  • quadrate lobe = bounded by GB and its bed on right, and umbilical fissure w ligamentum teres on its left (separating it from segment III) - contains portal fissure and the portal structures at its base looking from inf to superior
• Porta hepatis, Glisson’s Capsule and Plates
  
  • Porta hepatis = fissure in liver between quadrante lobe in front and caudate process & lobe behind; receives hepatic pedicle and two ligaments - teres and venosum
  • hepatic pedicle consists of portal vein posteriorly, hepatic artery anteromedially & CHD anterolaterally
  • Glisson’s capsule condenses around portal trinity structures and surrounds them as they enter the liver substance - thus each bile duct, hepatic artery, portal vein unit is surrounded by a fibrous sheath
  • 4 fibrous plates on surface of liver which are condensations of Glisson’s capsule
    
    • hilar plate = most important in surgery - incising junction between base of Sg4 & hilar plate = ‘lowering the hilar plate’; important step in exposure of extrahepatic bile ducts espec left hepatic duct
      
      • sheath of right portal pedicle extends off hilar plate like a sleeve into liver surrounding portal structures; whereas on left, only segmental structures are sheathed bc main poratl vein, proper hepatic artery & CHD aren’t close enough to liver to be enclosed in sheath
    • cystic plate = ovoid fibrous sheath on which GB lies
      
      • usu left behind in cholecystectomy
      • at posterior extent, narrows to become a stout cord that attaches to ant surface of sheath of right portal pedicle
      • latter = point of reference when wanting to expose ant surface of R portal pedicle; must divide this cord to do so
      • in severe chronic inflammation, cystic plate may beomce hsortened & thickened so distance between cystic plate & R portal pedicle much shorter than usu - R portal pedicle in danger during top down chole
    • umbilical plate
    • arantian plate
• relationships
  
  • ​bare area in contact w diaphragm & right adrenal gland
  • visceral surface related, w peritoneum intervening, to stomach, duo, hepatic flexure of colon & right kidney (may leave impressions)
    
    • to right of gastric impression a slight bulge, the omental tuberosity, is in contact w lesser omentum, which separates it from a similar eminence on body of pancreas
  • oesophagus makes shallow impression on posterior surface of liver
  • liver suspended by hepatic veins & IVC; hepatic veins entirely intrahepatic & enter vena cava while it is clasped in deep groove on posterior surface
• blood supply
  
  • arterial blood from hepatic artery
    
    • divides into right and left branches in porta hepatis
    • right branch passes behind CHD & in liver divides into medial & lateral sectoral branches
    • left branch divides into medial & lateral sectoral branches
    • sometimes CHA arises from SMA or aorta (instead of coeliac trunk), in which case it usu runs behind portal vein
    • RHA may arise from SMA (15%) and LHA from L gastric artery (20%) as aberrant or accessory arteries
  • venous blood carried to liver by portal vein
    
    • divides in porta hepatis into right and left branches which in turn give sectoral branches like the arteries
  • no communication between right and left halves of liver; even within each half the arteries are end arteries (hence infarction of the liver)
    
    • however, in presence of disease, there are often enough anastomoses w phrenic vessels (eg across bare area) to provide a collateral circulation that is sufficient to allow ligation of hepatic artery
• venous drainage
  
  • venous return differs in that it shows mixing of right and left halves of liver
  • 3 main hepatic veins drain into IVC
  • middle vein runs in plane between right and left halves of liver & receives from each
  • further laterally lie a right and left vein; middle frequently joins left v near vena cava
  • all veins have no extrahepatic course & enter vena cava just below central tendon of diaphragm
  • several small accessory hepatic veins enter vena cava below main veins, incl a separate vein from caudate lobe
  • some anastomosis between portal venous channels in liver & azygos system of veins above diaphragm across bare area of liver
• lymphatic drainage
  
  • to 3-4 nodes that lie in porta hepatis, which also receive lymphatics of GB
  • drain downwards alongside hepatic artery to pyloric nodes + directly to coeliac nodes also
  • lymphatics from bare area of liver communicate w extraperitoneal lymphatics which perforate diaphragm & drain to nodes in posterior mediastinum
  • similar communications exist along left triangular & falciform ligaments from adjacent liver surfaces
• innervation
  
  • sympathetic from coeliac ganglia, from which nerves run w vessels in free edge of lesser omentum & enter porta hepatis
  • vagal fibres from hepatic branch of ant vagal trunk reach porta hepatis via lesser omentum

Question 32

Mediastinum

Answer 32

• central compartment of the thoracic cavity
• divided into the superior and inferior mediastinum by the plane of Louis passing between the sternal angle and lower borrder of T4
• inferior mediastinum is divided into anterior, middle and posterior mediastinum by the fibrous pericardium
• anterior and posterior mediastinum are in direct continuity with the superior mediastinum; separation from it is purely descriptive not anatomical
• contents
  
  • heart and great blood vessels, oesophagus, trachea and its bifurcation, thymus, thoracic duct, lymph nodes, phrenic and vagus nerves and cardiac plexus
  • cardiac plexus has superficial part in front of ligamentum arteriosum; deep part larger and lies to right of ligamentum arteriosum, in front of bifurcation of trachea and behind aortic arch
    
    • receives sympathetic fibres from the 3 cervical and upper 4 or 5 thoracic sympathetic ganglia on both sides, parasympathetic fibres from both vagi in their cervical course and both recurrent laryngeal nerves
• superior mediastinum
  
  • wedge shaped; anterior boundary is manubrium, posterior boundary is bodies of first four thoracic vertebrae
  • contains:
    
    • at inlet, centrally trachea anteriorly and oesophagus posteriorly; apices of lungs lie laterally separated by trachea and oesophagus, and by vessels and nerves passing between neck and superior mediastinum
    • below the inlet trachea slopes back and manubrium slopes forward; brachiocephalic trunk, left brachiocephalic vein and thymus occupies this space
    • veins entering superior mediastinum = right and left brachiocephalic veins, each formed by confluence of int jug w SCV behind SCJ
      
      • confluence produces SVC behind lower border of first right costal cartilage; this passes vertically downwards behind right edge of sternum, anterior to right pulmonary hilum
    • concavity of arch of aorta lies in a plane of sternal angle & arch of aorta lies wholly in superior mediastinum, behind the manubrium
      
      • arches over beginning of left main bronchus and bifurcation of pulmonary trunk
      • brachiocephalic trunk begins as midline branch from aorta and diverges to right as it ascends in front of trachea
      • other 2 branches of arch, L CCA and LSCA pass upwards on left side of trachea
        
        • these keep left vagus nerve and apex of left lung away from contact w trachea; on right no structure to separate trachea from right vagus and apex of left lung
• plane of Louis passes through: concavity of arch of aorta, ligamentum arteriosum w left RLN recurivng below it, superficial and deep parts of cardiac plexus, just above pulmonary trunk, bifurcation of trachea, pretracheal fascia blends w pericardium over front of upper part of heart, azygos vein enters SVC, throacic duct reaches left side of oesophagus on its passage upwards from abdomen, prevertebral fascia fuses w anterior longitudinal ligament
• anterior mediastinum
  
  • lies between pericardium and sternum, overlapped by anterior edges of both lungs
  • contains thymus, sternopericardial ligaments, a few LNs and branches of int thoracic vessels
• middle mediastinum
  
  • contains pericardium and heart, w adjoining parts of great vessels, lung roots, phrenic nerves and deep part of cardiac plexus
• posterior mediastinum
  
  • bounded posteriorly by thoracic vertebrae 5 to 12 and anteriorly by pericardium and sloping fibres of diaphragm
  • continuous directly, via posterior part of superior mediastinum, w tissue spaces behind pretracheal fascia and in front of prevertebral fascia of neck
  • contents: oesophagus, thoracic aorta, azygos, hemiazygos and accessory hemiazygos veins, thoracic duct and lymph nodes
  • NB thoracic sympathetic trunk lies posterior to costovertebral plexura and therefore not a content of posterior mediastinum

Question 33

Oesophagus

Answer 33

• overview
  
  • 2-layered mucosal lined tube that travels thorugh neck, chest and abdomen and rests in posterior mediastinum
  • 25cm long, begins at cricoid C6, 15cm from incisors
    
    • cervical part (5cm); C6 to T1
    • thoracic part (18cm); T1 to T10
    • abdominal part (1-2cm); oesophageal hiatus –> GOJ
  • begins midline at C6
    
    • circular muscle = direct continuation of cricopharyngeus; long muscle attached to midline ridge of cricoid muscle and arytenoid cartilages
  • deviates slightly to left of trachea as it passes through neck into thoracic inlet (T1)
  • back to midline at T5 (where crossed posteriorly by thoracic duct)
  • deviates to LHS at T7 & curves forward (to pass in front of descending aorta)
  • pierces diaphragm at T10, 2.5cm to left of midline (encircled by right crus)
• relations
  
  • in neck:
    
    • posteriorly: prevertebral fascia
    • laterally: carotid sheath and thyroid (separated from thyroid by deep cervical fascia, under which also lie inferior thyroid arteries emerging from behind carotid sheaths)
      
      • RLN in TOG in 50% of cases
      • thoracic duct lies to left of oesophagus in region of thoracic inlet
    • anteriorly: lower part of larynx & trachea (first 1-2cm of oesophagus lies behind the larynx and isn’t easily separable from it)
  • in chest:
    
    • anteriorly:
      
      • trachea (with oesophagus slightly to left of it) until trachea branches into two main bronchi at T4
      • crossed by left main bronchus and right pulmonary artery just below bifurcation of trachea
      • below that, pericardium and posterior sloping fibres of diaphragm
    • posteriorly:
      
      • thoracic duct, at first to its right then ascending directly behind it at T5 and lying to its left in superior mediastinum/region of thoracic inlet; more proximally it passes laterally behind carotid sheath and out of field
      • on a more posterior plane, hemiazygous, accessory hemiazygous and right posterior (aortic) intercostal arteries cross midline behind oesophagus
      • pocket of right pleura behind oesophagus and in front of azygos vein and vertebral column (posterior to lower thoracic oesophagus the two pleural cavities almost touch so easy to enter opposite pleural cavity while dissecting)
      • descending aorta inferiorly
    • to right side of oesophagus
      
      • crossed by azygos vein at T4
      • mediastinal pleura
      • vagus
      • (the entire length of the right side of the oesophagus is related to the pleura, except where the azygos vein arching forward seaprates it; hence, division of the azygos vein and visceral pleura exposes the entire length of the thoracic oesophagus in the right thorax)
    • to left side of oesophagus:
      
      • crossed by arch of aorta
      • mediastinal pleura
      • vagus and left RLN
      • (aortic arch and its branches lie between oesophagus and pleura above, but below the arch the pleura is in direct relation to lower oesophagus)
    • laterally the vagus nerves cross oesophagus on their course to lie posterior to the root of the lungs, and after forming a plexus around the mid oesophagus they usu emerge as 2 or more trunks which come to lie anterior (mainly left vagus) and posterior (mainly right vagus) to the body of oesophagus
      
      • left RLN is also a lateral relation above the arch of the aorta; can be damaged during dissection from right chest where nerve lies medial to aortic arch and then between trachea and oesophagus more proximally
• constrictions (measured from incisors)
  
  • 15cm at commencement - cricopharyngeal sphincter (C6) - narrowest part
  • 22cm - crossed by aortic arch
  • 27cm - crossed by left main bronchus
  • 38cm - diaphragmatic hiatus (T10)
• HPZ at inlet of oesoph = UES
  
  • inf pharyngeal constrictor inserts into median raphe & is composed of thyropharyngeus & cricopharyngeus muscles that originate bilaterally from lateral portions of thyroid & cricoid cartilages respectively
  • cricopharyngeus part of inf pharyngeal constrictor = responsible for generating a HPZ that marks position of UES and oesophageal introitus
  • cricopharyngeus transitions into circular inner muscular layer
  • physiologically and morphologically, the UOS
• structure
  
  • non-keratinising stratified squamous epithelium; abruptly becomes glandular columnar (evident endoscopically at the Z line) either at or just above the GOJ
    
    • mucosa = 4 layers - epithelium, BM, LP, MM (fibres mainly running longitudinally)
  • submucosa - contains elastic and fibrous tisuse, usu regarded strongest layer of oesophagus for holding sutures; also contains neurovascular tissue (incl Meissner neural plexus)
  • muscularis propria - inner circular, outer longitudinal
    
    • longitudinal muscle arises from back of cricoid cartilage
    • circular muscle = continuation of cricopharyngeus muscle
    • striated muscle in upper part (incl cricopharyngeus); smooth muscle in lower & a mixture in middle (both smooth and striated comprise a single functional unit)
    • Auerbach plexus between muscle layers of oesophagus
  • no serosal layer (just perioesophageal tissue/adventitia)
• function
  
  • transit of liquid and food boluses from mouth to stomach
  • primary peristalsis: brainstem -> vagus N -> myenteric plexus
  • secondary peristalsis: initiated by stretch receptors from initial swallow
  • tertiary contractions: aberrant synchronous contractions w/o distension, non-functional peristalsis
  • modifiers: temp, volume, acid
• blood supply
  
  • UOS, cervical upper third = inferior thyroid artery
  • middle third = oesophageal arteries off thoracic aorta & bronchial arteries
  • distal third = ascending/oesophageal branches of left gastric
  • considerable overlap/dense submucosal plexus - all arteries that supply blood to oesophagus terminate in a capillary network before they penetrate muscular wall of oesophagus; after penetrating & supplying the muscular layers, cap network continues the length
  • NB inf thyroid arteries anastomose freely w superior thyroid arteries so ligation of an inf thyroid doesn’t appear to jeopardise blood supply to a cervical stump for oesophagoenteric anastomoses
  • there is also a rich intramural network of anastomoses in wall of oesophagus which communicate w anastomoses in wall of upper stomach, which is responsible for adequate vascularisation of an oesophageal anastomosis even though as much as 4 or 5cm has been mobilised from its bed
• venous drainage
  
  • through tributaries into azygos & hemiazygos system in chest, thyroid veins in neck and left gastric vein in upper abdomen
  • upper third: brachiocephalic veins (inf thyroid veins which are tributaries of brachiocephalics)
  • middle third: azygos & hemiazygos vein (2 hemiazygos veins join azygos behind oesophagus at T7/8)
  • inf third: left gastric vein –> portal vein
    
    • venous drainage of lower oesophagus is a watershed area between systemic and portal venous system and therefore is an area where varices develop in portal hypertension
    • there is a plexus of veins in the submucosa & also external to oesophagus and these are in communication via perforating veins
    • however, there is also a plexus of veins in region of lamina propria, i.e. a subepithelial plexus which is more or less limited to distal 5cm of oesophagus; is these veins which enlarge and bleed as varices
• lymph drainage
  
  • prox third –> deep cervical nodes –> thoracic duct
  • middle third –> superior and posterior mediastinal nodes
  • distal third –> left gastric A and coeliac plexus nodes
  • considerable interconnection of nodal drainage & bidirectional flow of lymph = responsible for spread of malignancy from distal oesophagus to prox oesophagus
    
    • distributed predominantly in form of a submucosal plexus & a paraoesophageal plexus, and both receive lymph from all the layers of the oesophageal wall; these plexuses communicate through penetrating vessels that traverse the longitudinal and circular muscle
  • plexuses tend to run longitudinally, often for long distances; explains the clinicopathological findings of satellite mets and submcusoal tumour deposits some distance from primary tumour in some pts w carcinoma of oesophagus
  • there are nodes assoc w oesophagus at all levels & although functionally continuous, they are loosely classified into anatomical groupings for destructive purposes, e.g. paratracheal, hilar, subcarinal, para-aortic, paraoesophageal etc
  • the free communication between various lymphatic channels means that in a small proportion of cases w cervical oesophageal cancer coeliac nodes will be involved & similarly in a small proportion of cases w lower third oesophageal cancers, cervical LNs will be involved
• nerve supply
  
  • upper: RLN (somatic) & SNS fibres from middle cervical ganglia
  • mid/lower
    
    • SNS: fibres from thoracic sympathetic trunk & greater splanchnic nerves
    • PSNS: vagus nerves –> plexus –> ant (mostly L vagus fibres) & post vagal trunks
  • vagus nerve
    
    • smooth muscle afferent fibres - respond to distension
    • mucosal afferent fibres - osmo/chemo/thermo and intra-luminal stimuli (pain related to pressure not visceral pain)
    • efferent fibres from nucleus ambiguous - UES & striated muscle motor function
    • efferent fibres from dorsal motor nucleus - smooth muscle motor function & secreto-motor innervation to glands
  • spinal nerves (T1-10)
    
    • afferent fibres from muscle act as nociceptors to intraluminal pain incl acid induced pain
    • cervical & thoracic sympathetic chains regulate vascular constriction, sphincter contractions, relaxation of muscular wall & increase glandular and peristaltic activity
  • multiple plexuses
    
    • Auerbach’s myenteric plexus - between circular & longitudinal muscle planes - contraction of outer muscle layers
    • Meissner’s submucosal plexus - regulates secretion & the peristaltic contractions of the muscularis mucosae
    • myenteric interstitial cells of Cajal - pacemaker cells throughout GIT responsible for slow wave contraction or smooth muscle

Question 34

Pancreas

Answer 34

Overview

• Pancreas is a mixed exocrine & endocrine gland situated in retroperitoneum of upper abdomen
• Resembles a side-lying hockey stick in shape; ~15cm long x 3.5cm wide x 1.5cm thick
• Average weight 75-125g
• Has a head, neck, body, tail, uncinate process
• Neck lies on transpyloric plane, L1
• Usually 2 ducts draining pancreas
  
  • Major duct of Wirsung which opens as major papilla, 10cm distal to pylorus in D2
  • Accessory duct of Santorini opens as minor papilla 2cm prox to opening of main duct
  • Significant variation in relationship between main and accessory duct
  • Major duct and CBD run parallel in HOP before joining to form ampulla of Vater

Relationships

• Head lies in C-shaped concavity of duodenum
• Posterior relations
  
  • from right to left: right kidney & perinephric fat, IVC and R gonadal vein, aorta, L renal vein (slightly inferior), retropancreatic fat, left adrenal gland, superior pole of L kidney
  • Posterior surface indented by and sometimes encloses, the CBD as it descends to enter the posteromedial duodenum
  • Posterior to head = IVC and both renal veins at level of L2
  • Posterior to neck of pancreas = SMV and splenic vein join to form portal vein
  • Splenic artery has a tortuous course above and below superior border of pancreas
    
    • Gives off dorsal pancreatic artery
    • Numerous smaller pancreatic branches
    • Great pancreatic artery/pancreatica magna
  • Splenic vein posterior to body and tail
• Lateral relations
  
  • Spleen – tail of pancreas heads to hilum in splenorenal ligament, lying anterior to left renal hilum
    
    • Tail of pancreas mobile and variable relationship with splenic hilum; tail of pancreas lies within 1cm of hilum in 70%, direct contact in 30%
    • Splenorenal ligament also contains splenic artery, origin of splenic vein & lymphatics
• Superior
  
  • Coeliac artery arises vertically superior to SMA close to superior edge of pancreas, where it gives off common hepatic & splenic arteries
    
    • Common hepatic runs anteriorly & to right above superior border of panc; at the point where it passes in front of portal vein, gives off GDA, which passes anterior to neck of panc, sometimes buried within it
  • Splenic artery has a tortuous course above and below superior border of pancreas
• Anterior
  
  • Anterior to neck of panc = GDA (sometimes buried within it)
    
    • Gives off anterior and posterior superior pancreaticoduodenal arteries & terminates as right gastroepiploic artery that arises in fold of tissue towards pylorus
  • Anterior to uncinate process: start of SMA and SMV
    
    • Middle colic, a branch of SMA, emerges from beneath pancreas to travel between leaves of mesocolon
  • Anterior surface of body & tail of panc covered in peritoneum of posterior wall of the lesser sac, and then by the posterior wall of the stomach anterior to this
• Inferior:
  
  • Transverse mesocolon (related to inferior border of pancreas, and R&L extremities of transverse colon are related to head and tail of gland
  • Transverse mesocolon divides into two leaves
    
    • Superior covering anterior surface
    • Inferior passing inferior to pancreas

Blood supply

• Consists of 2 vascular systems arising from celiac trunk & SMA
• Head & uncinate process = supplied by pancreaticoduodenal arcade
  
  • Superior (ant + post) pancreaticoduodenal a – off GDA
    
    • SPDA divides into ant & post branches as it runs inferiorly within pancreaticoduodenal groove
  • Inferior (ant + post) pancreaticoduodenal a – off SMA
    
    • IPDA divides into ant & post branches as it runs superiorly within pancreaticoduodenal groove
  • Terminal branches of these arteries join each other to form the arcade
• Splenic artery gives rise to ~2-10 pancreatic branches (gives rise to 3 main arteries in dorsal surface of gland) - supplies neck, body and tail
  
  • Dorsal pancreatic artery given off as first branch in region of neck (most medial of the 3 & most important)
    
    • Anastomoses w pancreatico-duodenal arcade in neck of pancreas)
    • Most aberrant artery in upper abdomen; can also arise from coeliac trunk or prox common hepatic artery
    • Continues towards region of inf border then runs laterally towards tail as inferior/transverse pancreatic artery
  • Greater pancreatic artery = prominent branch at ~junction of middle and distal thirds
  • Artery to tail of pancreas anastomoses with inferior pancreatic artery

Venous drainage

• follows arterial supply - splenic vein, gastrocolic trunk and posteroinferior pancreticodudenal vein into SMV, anterior and posterior superior pancreaticoduodenal veins into PV

Lymph drainage

• to splenic hilum/gastrosplenic omentum (left gland)
• gastroduodenal LNs (right superior)
• infrapancreatic lymph nodes (right inferior)
• retropancreatic LNs to celiac & superior mesenteric nodes

Innervation

• Highly innervated visceral organ
• Panc nerves are sensitive to both chemical & mechanical stimuli
  
  • These nerves transmit nociceptive & visceral afferent signals to coeliac plexus, which is largest of 3 plexuses of sympathetic system
• Normally, the preganglionic efferent fibres exit spinal cord to form the sympathetic chain
  
  • Instead of synapsing at sympathetic chain, the greater, lesser and least splanchnic nerves pass through sympathetic chain to form coeliac ganglia, and provide the major preganglionic contribution to coeliac plexus
  • Coeliac plexus most commonly consolidates around origin of coeliac axis and SMA
• Parasympathetic supply of panc = from left & right vagal trunks, which don’t connect at coeliac ganglia
• Coeliac plexus block used to treat pain in chronic pancreatitis

Question 35

Spleen

Answer 35

• overview
  
  • haematological organ located in LUQ, completely covered by ribcage
  • 1x3x5 inches, weighs 7oz (~200g), lies between ribs 9-11 with long axis along line of 10th rib
  • size of a clenched fist; must become at least twice its normal size before becoming palpable
  • has one pedicle running from superoposterior border of pancreas to its hilum containing the splenic artery and vein
• structure
  
  • has a capsule from which trabeculae extend into parenchyma
  • red pulp contains:
    
    • Billroth cords amongst reticulin fibres, w scattered macrophages
    • venous sinusoids
  • white pulp = local expansions of lymphocytes scattered throughout red pulp
    
    • closely assoc w central arterioles that are surrounded by periarterial lymphatic sheaths containing T lymphocytes (Periarteriolar lymphoid sheath = ‘PALS’)
    • B cells form follicles (+/- with central germinal centres) that surround T lymphocytes
      
      • in response to antigen presentation, these B lymphocytes become activated & produce antibodies that play signif role in opsonisation of extracellular organisms incl encapsulated organisms
    • perifollicular/marginal zone at periphery, which blends w red pulp
      
      • vascular spaces of marginal zone between red & white pulp channel blood into splenic Billroth cords & out into sinuses
      • contain antigen-presenting cells crucial for initiating lymphocyte activation
  • major vasc outflow from spleen occurs via coalescence of open sinuses via reticualr trabeculae into splenic vein
  • spleen invested by 2 fibrous capsules
    
    • outer tunica serosa - derived contiguous w peritoneum & invests organ except at hilum, where peritoneum reflects into the phrenicocolic and gastrosplenic ligaments
    • tunica albuginea - invests entire organ & at hilum reflected inward along vessels to form sheaths from which trabecular framework of spleen emanates
• functions
  
  • haematopoietic
  • reservoir
  • filtration
  • immunity
• surfaces/attachments
  
  • 2 surfaces
    
    • diaphragmatic = smooth & convex, lies against diaphragm
    • visceral = irregular & concave with impressions contacting fundus of stomach, left kidney, splenic flexure of colon, tail of panc
  • 4 ligamentous attachemtns of spleen, 3/4 of which are avascular
    
    • spleno-colic
    • spleno-renal - contains splenic artery & vein and tail of pancreas; some say splenorenal ligament itself is posterior to these
    • spleno-phrenic
    • gastrosplenic - carries short gastrics from splenic hilum to lateral stomach, and left gastroepiploic in inferior aspect
    • note also phrenicolic ligament which connects left colic flexure & diaphragm, also supports diaphragmatic surface of spleen
  • from practical point of view assume there will be adhesions between inferior medial aspect of spleen and greater omentum
• relationships
  
  • splenic flexure overlies inferior pole
  • pancreatic tail abuts spleen in 30%
  • superior pole of spleen & greater curvature of stomach v close to each other - may be <1cm apart as gastrosplenic lig v short –> need great care in dissection to avoid injury to stomach or devascularise the short gastrics
  • anterior to left kidney
• blood supply
  
  • splenic artery
    
    • divides before entering hilum into multiple branches
    • 2 common variants of splenic artery
      
      • distributed type gives off branches early & distant from hilum (70%) - usu a Y-shaped division
      • magistral type branches into terminal and polar arteries near hilum of spleen (30%) - more a T-shaped division (in both instances w the Y and T lying horizontally, and the branches to the spleen come off inside of Y or outside the bar of the T
    • splenic artery branches into ~5-6 polar arteries & 6 short gastric arteries
      
      • superior polar artery which sometimes communicates w short gastric arteries, superior, middle and inferior terminal arteries, and inferior polar artery
    • ramify throughout organ radially into splenic arterioles that branch into pencillar arterioles that ultimately terminate in splenic cords; here the reticuloendothelial cells & splenic macrophages come in intimate contact w blood and its contents as it percolates through splenic cords & across walls of splenic sinuses
    • so spleen divisible into well delineated segments based on its blood supply - there are upper and lower polar segments and 1-5 central segments
      
      • relevant for splenic preservation; division of segmental arteries can be carried out in the performance of partial splenectomies
      • in ~40% of cases the artery to the upper polar segment arises well proximally from the main splenic or its upper division
      • ~75% of inferior polar arteries arise proximally and ~half of these arise from left gastroepiploic artery
• venous drainage
  
  • splenic vein
    
    • created by union of several splenic veins & left gastroepiploic vein
    • confluence of 2-6 tributaries usu occurs in splenorenal ligament and as with arteries and upper or lower polar vein often exits separately to join splenic vein at a considerable distance away from spleen
    • splenic vein or one of its major tributaries receives left gastroepiploic vein
    • short gastric veins drain by penetrating the splenic substance rather than draining into splenic vein outside spleen
    • travels posterior to pancreas, collects 3-13 pancreatic veins from anterosuperior surface & often IMV to join SMV to form portal vein
• lymphatic drainage
  
  • into several nodes lying at hilum, and thence, by way of pancreaticosplenic nodes, to the coeliac nodes
• innervation
  
  • by coeliac plexus with sympathetic fibres only

Question 36

Stomach

Answer 36

Overview

• main parts = fundus, body, pyloric part; greater & lesser curvatures form left & right borders
  
  • fundus = part above cardia
  • body = goes from fundus down to angular incisura (notch on lesser curvature seen radiologically or anatomically the region where the vessels and nerves of lesser omentum are seen to fan out as the ‘crow’s foot’)
  • pyloric part goes from line at 45 degrees to vertical between incisura to gastro-duodenal junction; proximal pyloric antrum narrows distally as pyloric canal
  • circular muscle at distal end of canal = thickened to form pyloric sphincter, whose position is indicated on anterior surface by prepyloric vein (of Mayo)
  • pyloric canal lies on head & neck of pancreas
• GOJ = cardia = most fixed part of organ – 2.5cm to left of midline at T10 behind 7^th costal cartilage, 40cm from incisors
• Gastroduodenal junction = pylorus = in recumbent positon usu a little to right of midline at L1

Structure

• Mucosa
  
  • Division between body and antrum corresponds w a histological division of the stomach, w parietal cells and chief cells occurring predominantly in the fundus and body and gastrin-producing cells occurring predominantly in the antrum
    
    • But level to which a band of antral mucosa rises along lesser curvature of stomach is variable and can reach as high as the GOJ
  • Cardia = junctional mucosa – mainly mucus cells and glands, usu covers an area of ≤2cm in length and mucosa usu persists for 1-2cm into oesophagus where it joins the squamous mucosa at an irregular interface called Z line
  • This junctional mucosa may actually be metaplastic epithelium as a result of the action of gastric juice on lowermost squamous mucosa of oesophagus
• Musculature
  
  • Outer longitudinal coat and inner circular and oblique fibres
  • Oblique of greatest importance in region of cardia and lesser curve; sweep around fundus at the point of entry of the oesophagus and prob play a role in maintaining acute angle of entry of oesophagus – angle of His
    
    • May also be responsible by their contraction for directing some oral intake down the lesser curvature of the stomach
  • When muscle fibres reach pylorus they tend to end in a fibrous septum – at least on anterior inferior and posterior surfaces; on lesser curve they are more likely to be continuous w duodenal muscle fibres
  • Muscle coat and in particular the circular muscle coat is thickest in antrum
• Pylorus
  
  • Has complex anatomical structure
  • On greater curve of stomach, circular muscle thickens to form 2 discrete muscle loops: prox and distal pyloric sphincters
    
    • These loops define the anatomical borders of the pylorus & enclose a sheet of circular muscle between them
  • The distal sphincter or loop exists for only a short distance at the narrowest point of the GD junction and is thus quite distinct
  • Prox sphincter is less prominent, occurring over a longer segment of the greater curvature
  • The 2 sphincters are clearly separated only on the greater curve aspect, while on the lesser curve they fuse w the circular muscle of the pyloric channel to form a muscular knob known as pyloric torus
  • Distal sphincter and torus form thickest portion of Gastroduodenal junction & are generally regarded as main pyloric sphincter
  • Ends abruptly w a clear-cut change to much thinner duo musculature
  • Lumen can be widened greatly by dividing the pyloric region longitudinally & sewing it up transversely (pyloroplasty)
  • Can also attenuate function by
    
    • Removing part of its muscle anteriorly (pyloromyomectomy)
    • or dividing muscle longitudinally (pyloromyotomy)
    • With both techniques care and patience required in dividing muscle as it is easy to perforate duo mucosa

Blood supply

• Typically arises from 3 major branches of coeliac axis – the hepatic, splenic and left gastric arteries, however a small supply to prox stomach can come through oesophageal arteries directly from aorta
• Important feature of blood supply is rich anastomosing networks which exist in gastric wall at 3 levels; mucosally, submucosally and intramuscularly
  
  • Well developed everywhere except along lesser curve of stomach where anastomosing channels are of finer calibre and more of the arteries of supply appear to be end arteries
• Fundus and upper left part of greater curvature = supplied by short gastrics, branches of the splenic, which run in gastrosplenic ligament
• Lesser curvature = supplied by L gastric artery & R gastric artery (a branch of hepatic or GDA), which run between 2 layers of lesser omentum
• Greater curvature is supplied by left gastro-epiploic artery (a branch of the splenic) and the right gastro-epiploic artery (a branch of GDA) which run between the 2 layers of greater omentum 1cm from gastric wall (right is closer to greater curve than left)
• Both sets of arteries anastomose w each other on their respective gastric curves and then again w the supply of the other curve via a rich anastomosing network at 3 levels within the gastric wall:
  
  • mucosal, submucosal, intramuscular
  • NB these networks are well developed everywhere except along lesser curve where anastomosing channels are of finer calibre & more of arteries of supply appear to be end arteries
• NB a branch from the splenic artery, as it runs along upper border of pancreas, the posterior gastric artery, may also supply the stomach – present in 62%
• Can sacrifice:
  
  • Short gastrics
  • Left gastric
  • Left gastro-omental/epiploic
• Must maintain:
  
  • Right gastric
  • Right gastro-omental/epiploic
• NB doesn’t supply stomach but relevant to operative anatomy is that aberrant left hepatic artery originates from left gastric artery in 20% of cases – runs in lesser omentum
• Left gastric
  
  • Usu from main trunk of coeliac but occasionally directly from aorta
  • Passes upwards & to left then forwards to ~GOJ or a little below on lesser curve of stomach
  • Tends to raise fold of peritoneum – gastropancreatic fold
  • Gives off oesophageal branches & turns downwards & usu divides into ant & post branches which supply appropriate walls of stomach
  • Anomalies
    
    • In 20-30% cases a left hepatic artery arises from left gastric & this courses trough lesser omentum to left side of liver
    • Accessory left gastric in 10% - arises from splenic artery & travels in bare area to stomach; like a posterior gastric but more to right & travels to lesser curve
• Right gastric
  
  • From hepatic artery before or after it has given off GDA
• Left gastroepiploic
  
  • From splenic artery à passes forward in short splenorenal ligament then gastrosplenic ligament to reach greater curve of stomach at ~level of lower pole of spleen
  • Then runs in greater omentum ~1cm from greater curve
  • Gives off some short gastrics to fundus as it passes forwards
  • Also ant & post branches from the arcade & gives off branches to omentum
• Right gastroepiploic
  
  • Arises as one of the 2 terminal branches of GDA, after GDA has passed behind D1 – mirror image of left
• Short gastrics & posterior gastric artery
  
  • Short gastrics arise either from splenic artery or its branches & pass forward in gastrosplenic ligament to supply fundus
  • Posterior gastric artery = quite like most prox short gastrics & is present in majority; arises from splenic artery & arches forwards over top of lesser sac to reach stomach through bare area

Gastrectomy procedures and blood supply

• For distal gastrectomy procedures there is obviously an abundant blood supply to remaining stomach from left gastric, posterior gastric and short gastric arteries
• But as amount of stomach taken starts to increase some care necessary
  
  • Thus for a high partial gastrectomy the left gastric artery and some of the short gastric arteries are usu divided
  • If all of short gastric arteries and the posterior gastric artery are divided then remaining stomach has to live on supply from oesophagus and v occasionally from the left phrenic artery; this degree of devascularisation doesn’t automatically mean the stomach remnant will necrose, but is prudent for the surgeon to make sure the wall looks a normal colour and that the edges are bleeding – if any doubt then total gastrectomy
  • If procedure being performed for benign disease then left gastric should be transected close to stomach in order to retain the ascending branches to cardia and oesophagus
  • For prox partial gastrectomy there is again no problem bc of the blood supply from the right gastric and right gastro-epiploic arteries
• Gastric transposition procedures and formation of gastric tubes
  
  • The use of the stomach to replace the oesophagus has increased in popularity in recent yrs
  • Stomach is mobilized from all vascular structures except right gastric and right gastroepiploic pedicles
  • Mobilisation of greater curve undertaken w great care in order to maintain the gastro-omental arch; if arch deficient the blood supply can sometimes b maintained by preserving the greater omentum with its right and left omental arteries, providing vascular continuity
  • Initially was thought it might be important to ligate left gastric artery close to its origin in order to maintain a sort of right/left gastric arch
  • But experience has shown that not the case and may even be preferable to resect most of the lesser curve (which makes stomach into a tube) as the lesser curve is more susceptible to ischaemia than other areas of the stomach
  • W the formation of isoperistaltic gastric tubes the greater curvature and fundus are reliant on blood supply from right gastroepiploic artery alone
  • While it is true that most often this blood supply is sufficient, no doubt that procedure of stretching the stomach up to the nec for an anastomosis puts added strain on an adequate blood supply and has been suggested the distal-most 20% of the tube (ie approx. the fundus) should be discarded on the grounds that its blood supply is often marginal
  • Reversed gastric tubes have been used less frequently, w their blood supply being based on the left gastric artery and splenic artery

Venous drainage

• Veins of same name accompany arteries & drain into portal vein itself or into splenic or SMV
• Left gastric vein tends to lie in the angle between the hepatic artery and the splenic artery and is usu encountered before the left gastric artery when approached from below
• Prepyloric vein (unaccompanied by an artery) drains into right gastric vein

Relations

Stomach bed

• Posterior wall of stomach = covered by peritoneum of ant wall of lesser sac, and bed is covered by lesser sac’s posterior wall
• Left crus & dome of diaphragm
• Splenic artery
• Body of pancreas
• Upper part kidney
• Adrenal
• Transverse mesocolon
• Spleen
• Left colic flexure
• To right of lesser curvature in midline lies aorta & coeliac trunk, coeliac plexus & ganglia and coeliac LNs

NB stomach lies in front of much of the lesser sac but posteriorly the peritoneum leaves the stomach, at a variable, point, leaving the posterior aspect of the fundus bare of peritoneum

• is through here that the posterior gastric artery passes to the stomach and also the left gastric vessels, though they are often at a more inferior point and are contained in their own peritoneal fold – the superior gastro-pancreatic fold

Question 37

Carpal tunnel

Answer 37

Overview

• Passageway on the palmar side of the wrist that connects the forearm to the hand
• The tunnel is bounded by the carpal bones and flexor retinaculum

Boundaries

• Proximal limit = at distal dominant wrist crease
• Anterior: flexor retinaculum
  
  • 2-3mm transversely & longitudinally
  • Fibrous band attached
    
    • Radially to tubercle of scaphoid & ridge of trapezium
    • Ulnar side to pisiform and hook of hamate
    • Radially it divides with the superficial lamina inserting into the scaphoid and trapezium and the posterior lamina inserting into the posterior tip of the groove in the trapezium in which runs the tendon of FCR; this tendon therefore has its own compartment
  • Several structures cross superficial to the FR; from medial to lateral
    
    • Superficial branch of ulnar nerve and ulnar artery (lie in small canal of Guyon w artery lateral to nerve)
    • Tendon of palmaris longus (blends with FR and also contributes fibres to palmar aponeurosis which is attached distally to FR)
    • Palmar cutaneous branch of median nerve
    • Origin of thenar muscles (partly arise from FR)
• Posteriorly & laterally = carpal bones
  
  • lateral to medial with proximal row first
    
    • Some lovers try positions that they can’t handle
    • Scaphoid lunate triquetrium pisiform trapezium trapezioid capitate hamate

Contents

• Median nerve
  
  • Immediately deep to FR, lying in front of the tendons
  • In this position lies behind and slightly to radial side of PL (which is absent in small number of cases)
  • At distal margin of FR, gives off a branch to the thenar muscles which tends to curve back to enter the muscles
• Long flexors of fingers and thumb: flexor digitorum superficialis and profundus, and flexor pollicis longus
  
  • FDP tendons lie deeply in 1 plane, with only the tendon to the index finger being separate from the others which remain attached together til they reach the palm
  • FDS tendons lie in 2 planes, superficial to FDP tendons
  • All 8 tendons of FDS and FDP share a common flexor sheath which doesn’t invest them completely but is reflected from their radial sides, where arteries of supply gain access
  • FPL lies in its own synovial sheath as it passes through the fibro-osseous tunnel
• Flexor carpi radialis
  
  • At lateral end of tunnel a deep lamina from FR is attached to medial lip of the groove on trapezium; FCR tendon enclosed in its own synovial sheath runs in groove in this subcompartment of carpal tunnel

Important structures in carpal tunnel surgery

• Median nerve
• Palmar cutaneous branch of median nerve
• Recurrent branch of median nerve
• Superficial palmar arch
• Ulnar nerve as it passes through flexor retinaculum

Question 38

Cubital fossa

Answer 38

Overview

• Area of transition between anatomical arm and forearm
• Located as a depression on ant surface of elbow joint

Borders

• Triangular in shape with 3 borders:
  
  • Lateral = medial border of brachioradialis
  • Medial = lateral border of pronator teres
  • Superior = imaginary line between epicondyles of humerus
• Floor = proximally by brachialis; distally by supinator
• Roof = deep fascia of forearm, reinforced by bicipital aponeurosis medially
• Within roof runs median cubital vein, which can be accessed for venepuncture (with median cutaneous nerve of forearm)

Contents

• Lateral to medial (Really need beer to be at my nicest)
  
  • Radial nerve – not always strictly considered part of cubital fossa, but is in vicinity, passing under brachioradialis; as it does so, radial nerve divides into its deep and superficial branches (posterior interosseous & superficial branch)
  • Biceps tendon – runs through cubital fossa, attaching to radial tuberosity, just distal to the neck of the radius
  • Brachial artery – supplies oxygenated blood to forearm; bifurcates into radial & ulnar arteries at apex of cubital fossa
  • Median nerve – leaves cubital fossa between two heads of pronator teres; supplies majority of flexor muscles in forearm

Question 39

Kidneys

Answer 39

Overview

• paired retroperitoneal organs mostly covered by the ribs with just their lower poles below the costal margin
• on the left the renal hilum is at L1, on the right L2
• have an oblique lie in both the sagittal and coronal axis due to the presence of psoas medially
• most kidneys measure 3x6x12cm and weigh 150g
• surrounded by a variable layer of peri-renal fat which in turn is surrounded by Gerota’s fascia

Relationships

• surmounted by adrenals on each side
• anterior relations on left:
  
  • descending colon and its mesentery
  • tail of the pancreas anterior to the hilum; lienorenal ligament passes from tail of pancreas and kidney to spleen at this point
• anterior relations on right:
  
  • ascending colon and its mesentery
  • D2 anterior to the hilum
• Upper pole of right kidney indents visceral surface of liver
• Each kidney provides a ureter at the renal pelvis, where the major calyces coalesce to form a funnel, the pelvicoureteric junction

Blood supply

• Renal arteries at L2 which are usually one in number on each side though accessory arteries from aorta may persist, reflecting the migration of the kidney upwards in foetal development

Venous drainage

• Via the renal veins; left significantly longer than right
• Left renal vein receives left gonadal vein at a right angle
• On right the gonadal drains directly into IVC

Lymphatic drainage

Innervation

• Splanchnic and vagus nerves

Question 40

Testes

Answer 40

Overview

• Oval organ ~5x2.5x3cm with thick covering of fibrous tissue = tunica albuginea
• Epididymis attached to posterolateral surface
• Vas deferens arises from lower pole of epididymis and runs up medial to it behind testis
• Front and side of testis lies free in serous space formed by overlying tunica vaginalis, serous membrane which is a remnant of processus vaginalis
  
  • Also covers anterolateral part of epididymis & liens a slit-like space, sinus of epididymis, which lies between testis & epididymis
  • Appendix testis = minute sessile cyst attached to upper pole of testis within tunica vaginalis; a remnant of paramesonephric duct
• Testis, epididymis & tunica vaginalis lie in scrotum surrounded by thin membranes, adherent to each other, that are downward prolongations of the coverings of spermatic cord
• Right and left sides separated by medial scrotal septum

Structure

• Upper pole of epididymis attached high up on posterolateral surface of testis
• Here there is a fibrous mass; mediastinum testis – from which septa radiate to reach tunica albuginea
  
  • Septa divide testis into 200-300 lobules, each of which contains 1-4 highly convoluted seminiferous tubules
  • Seminiferous tubules open into rete testis, a network of intercommunicating channels lying in mediastinum testis
  • From the rete, 12-20 vas efferentia enter commencement of canal of epididymis, thus attaching head of epididymis to testis
• Seminiferous tubules have several layers of cells
  
  • Outermost layer = spermatogonia, which divide to produce primary spermatocytes; these divide to form secondary spermatocytes, which have v short life and divide almost immediately to form spermatids; these don’t divide but undergo a metamorphosis into spermatozoa (whole process of producing spermatozoa from spermatogonia = spermatogenesis)
  • Among developing germ cells = supporting or sustenacular cells (of Sertoli) – secrete androgen binding protein which keeps a high conc of testosterone in germ cell environment
  • Scattered among cells of connective tissue between the tubules (outside them) = interstitial cells of Leydig – larger than fibroblasts, constitute endocrine portion of testis & secrete testosterone
• Apart from spermatozoa, testis makes only a small (10%) contribution to semen (seminal fluid); 60% from seminal vesicles and 30% from prostate

Blood supply

• Testicular artery from aorta runs in spermatic cord, gives off a branch to epididymis & reaches back of testis where it divides into medial & lateral branches
  
  • These don’t penetrate mediastinum testis but sweep around horizontally within tunica albuginea; branches from these vessels penetrate substance of organ
  • In region of epididymis, there is an anastomosis between testicular, cremasteric & ductal arteries; but if main artery is divided, smaller vessels may not completely sustain testis & atrophy may occur – though ischaemic necrosis unlikely

Venous drainage

• Venules reach mediastinum, from which several veins pass up in spermatic cord as mass of intercommunicating veins = pampiniform plexus, which surrounds testicular artery
  
  • In inguinal canal the plexus separates out into 4 veins which join to form 2 that leave the deep ing ring, becoming single on psoas major on posterior abdo wall
  • Left vein joins left renal vein at right angle; right drains directly into IVC at acute angle
• Testicular veins usu have valves
• Varicocele (varicosities of pampiniform and cremasteric veins) occurs much more frequently on left than right

Lymph drainage

• With testicular artery to para-aortic nodes lying alongside aorta at level of origin of testicular arteries (L2 vertebra)
• Testicular lymph doesn’t drain to ing nodes but overlying scrotal skin does

Nerve supply

• Testis supplies by sympathetic nerves – most of connector cells lie in T10 segment of cord
  
  • Passing mainly in lesser splanchnic nerve to coeliac ganglia the efferent fibres synapse there
  • Postganglionic grey fibres reach testis along testicular artery
• Sensory fibres share same sympathetic pathway – run up along testicular artery & through coeliac plexus & lesser splanchnic nerve and its white ramus to cell bodies in posterior root ganglion of T10 spinal nerve

Epididymis and Vas deferens

• Epididymis = firm structure attached behind testis w vas deferens to medial side
  
  • Consists of a single highly coiled tube packed together by fibrous tissue
  • Epithelial lining of the coiled tube is columnar with long microvilli called stereocilia; thin wall has a single layer of circular smooth muscle
  • Has a large head at its upper end, connected by a body to a pointed tail at its lower end
  • Head is attached to upper pole of testis by vasa efferentia & tail to lower pole by loose connective tissue
  • Body is partly separated from testis by a recess which is open laterally; the sinus of the epididymis
  • Lateral surface of epididymis is covered by tunica vaginalis, which also lines sinus
  • Blood supply: branch of testicular artery (anastomoses w tiny artery to ductus); venous & lymphatic drainage same as testis
  • Nerve supply: like testis by sympathetic fibres from coeliac ganglion via testicular artery
• Vas deferens = direct continuation of canal of epididymis from tail, passes up medially, thick wall of smooth muscle, enters spermatic cord, passes through inguinal canal, across sidewall of pelvis just under peritoneum & crosses pelvic cavity à pierces prostate & opens by ejaculatory duct into the prostatic urethra

Question 41

Ureter

Answer 41

Overview

• smooth muscle tubular structure that propels urine from the kidneys to the bladder
• in adult 25-30mm in length, 4mm diameter

Course

• arise from the renal pelvis (on the left the renal hilum is at L1, on the right L2), and descend towards the bladder on the anterior surface of psoas major muscle
• cross the pelvic brim then run posteroinferiorly on the lateral walls of the pelvis, and curve anteromedially to enter the posterior aspect of the bladder at the vesicoureteric junction
• divided into an abdominal part and a pelvic part
• abdominal part lies behind the peritoneum, on the medial part of the psoas muscle, crosses the genitofemoral nerve and is crossed by the gonadal vessels
  
  • right ureter: at its origin is covered by the duodenum (descending part), lies lateral to the IVC and is crossed by the right colic & ileocolic vessels
  • left ureter is lateral to inferior mesenteric vessels, is crossed by the left colic vessels and passes posteriorly to the apex of the sigmoid mesocolon at the pelvic brim
• enters the pelvis by crossing the division of the common iliac vessels
• pelvic part runs downward on lateral wall of the pelvic cavity, along the anterior border of the sciatic notch
  
  • lies anterior to hypogastric artery and medial to obturator nerve
  • inclines medially and enters the bladder at the lateral angles of the trigone
• prior to entering the bladder they are crossed superficially by
  
  • uterine arteries in women (water under the bridge)
  • vas deferens in men
• entry into the bladder is oblique, forming a valve system that prevents vesicoureteric reflux

From the PUJ, the ureters descend on psoas, under the psoas fascia, towards the pelvis approximating the tips of the vertebral transverse processes on xray. They are crossed superficially by the gonadal vessels from medial to lateral. At the pelvic brim, the ureters are located superficial to the bifurcation of the common iliac artery. They then course on the lateral pelvic side wall and turn medially (at the level of the ischial spines on xray) to enter the posterolateral apex of the trigone of the bladder on each side. Prior to entering the bladder they are crossed superficially by the vas in the male and the uterine artery in the female. The entry of the ureter into the bladder is oblique, forming a valve system that prevent vesicoureteric reflux .

Relationships

• anterior relations include:
  
  • right ureter – duo, right gonadal artery, right colic artery, ileal mesentery
  • left ureter – left gonadal artery, left colic artery, sigmoid mesentery
• posterior relations include: psoas muscle, genitofemoral nerve, sacroiliac joint, bifurcation of CIA
• Points of narrowest calibre:* 1) PUJ, 2) where it crosses pelvic brim, 3) as it passes through bladder wall
• Surface markings:* tip of 9^th costal cartilage à bifurcation of CIA (found by joining point of bifurcation of aorta (2cm below and to left of umbilicus) to a point midway between ASIS and pubic symphysis; CIA bifurcates 1/3 of the way down this line)
• Lines of projection on xray:* medial to tips of transverse processes of lumbar vertebrae à crosses pelvic brim at sacroiliac joint à then to ischial spine à then, foreshortened, to pubic tubercle

Blood supply

• segmental, from branches of: renal, aorta, gonadal, common and int iliac, superior and inferior vesical arteries and uterine artery

Venous drainage

• vein of ureter drain into renal, gonadal and internal iliacs

Lymphatic drainage

• run along arteries
• abdominal portion drains into para-aortic nodes below renal arteries
• pelvic portion drains into nodes on side-wall of pelvis

Innervation

• inferior mesenteric, spermatic, pelvic plexuses (autonomic)
• (?splanchnic and vagus nerves)
• pain fibres accompany sympathetic nerves
• T11-L2 sympathetic fibres reach ureter via coeliac and hypogastric plexus, together with parasympathetic fibres from pelvic splanchnic, but function unknown

How do you protect the left ureter in surgery?

• Right ureter lies protected behind duo, whereas left has no such structure; should thus be identified in any abdominal and pelvic surgery to avoid iatrogenic injury, which most commonly occurs near the lower pole of the kidney on the left or in the pelvis
• In malignancy of inflammatory disease processes, the ureter can be pulled up towards the diseased section and be injured within dissection planes if not already identified
• Identification best done initially from the lateral side of the colon, in an area unaffected by any pathology
• Then needs to be traced along its entire length where any dissection may be taking place
• If one undertakes this approach, important not to strip the periureteric tissue as you can interrupt the blood supply

Question 42

Vas deferens

Answer 42

• The vas is the continuation of the epididymis and starts at the lower pole of the testis
• It ascends within the spermatic cord and travels into the pelvis via the superficial then deep inguinal rings
• Passes along side wall and floor of pelvis to reach back of bladder
• During its course, no other structure intervenes between it and the peritoneum it is under
• On its way from the inguinal ring to the bladder it crosses the obliterated umbilical artery, the obturator nerve and artery, and the ureter lying on the obturator fascia
• Upon reaching the bladder, the duct then turns downwards and dilates in a fusiform manner into the ampulla, the storehouse of spermatozoa
• The ampulla lies parallel w spermatic vesicles and fuses w it terminally to form the ejaculatory duct
• These open through the prostate onto the verumontanum

Question 43

Clavipectoral fascia

Answer 43

Arises from clavicle enclosing subclavius muscle then descends to enclose pec minor and finally attaches to floor of axilla

Like pec minor lies anterior to neurovascular structures of the axilla

Question 44

Pec minor

Answer 44

• 3rd-5th ribs
• deep to pec major to insert into coracoid process
• nerve - mainly medial pectoral nerve (from medial cord)

Question 45

Pec major

Answer 45

• medial half clavicle, lateral half of sternum, 2nd-6th costal cartilages & aponeurosis of external oblique
• tendinous insertion into lateral lip of intertubercular groove of humerus
• medial and lateral pectoral nerves

Question 46

Spaces of hand

Answer 46

• Flexor tendon space
  
  • Synovial sheaths commence at distal transverse palmer crease to distal phalanges.
  • Make 2 incisions; one at the base of the pulp and one at the base of the proximal phalynx and irrigate
• Mid-palmer space
  
  • Dorsal to space are middle and ring finger metacarpels and volar to space are flexor tendons and lumbricals
  • Incise at the levels of the distal transverse palmar crease. Pass artery clips into lumbrical sheaths to ensure drainage
• Thenar space
  
  • Dorsal to space is adductor pollicus, volar to space are the index flexor tendons
  • Incise in web space between thumb and index finger
• Space of Parona
  
  • Space between pronator quadratus and flexor digitorum profundus
  • Longitudinal incision radial side of Ulnar pulse

Question 47

Serratus anterior

Answer 47

• digitations of outer surface of 1st-8th ribs
• fibres pass backwards to insert along whole of medial border of scapula
• holds scapula to chest wall
• long thoracic nerve

Question 48

subscapularis

Answer 48

• costal surface of scapula
• inserts into lesser tuberosity of humerus
• stedies hed of humerus against glenoid cavity & assists in medial rotation
• upper and lower subscapular nerves from posterior cord which come off either side of thoracodorsal

Question 49

Teres major

Answer 49

Inferior angle of scapula to medial part of intertubercular groove of humerus

supplied by lower subscapular nerves from posterior cord

Question 50

lat dorsi

Answer 50

lowermost 3-4 ribs, spinous processes of lower 6 thoracic vertebrae, lumbosacral vertebrae and iliac crest

spirals around lower border of teres major to insert into intertubercular groove of humerus

supplied by thoracodorsal nerve from posterior cord

Question 51

Axillary vein

Answer 51

• continuation of basilic vein which changes its name at lower border of teres major
• ascends at first medial to ax artery and more proximally lies medial and inf to ax artery until it reaches first rib where it becomes subclavian vein as it leaves axilla anterior to 3rd part subclavian artery
• relations
  
  • distally overlapped by biceps but mostly is a subcut structure w only the medial cutaneous nerve of the arm lying medial to it
  • brachial plexus structures lie lateral to it between it and ax artery - from distal to prox, medial cutaneous nerve of forearm and ulnar nerve, then medial cord of brachial plexus and proximlly medil pectoral nerve
  • long thoracic nerve runs posteriorly in axilla on medial wall, deep to fascia on serratus anterior and runs behind axillary vein
  • thoracodorsal nerve runs behind axillary vein & initially posterior nd medial to subscapular artery; these 2 structures then run down lat dorsi
  • lateral cutaneous brnch of 2nd intercostal nerve (intercostal nerve) lies below ax vein as it crosses axilla
  • medial pectoral nerve from medial cord passes between ax artery and vein then unites in front of ax artery w filament from lateral nerve before entering pec minor
• tributaries
  
  • 1st part:
    
    • cephalic vein (instead of superior thorcic as with artery) - enters by piercing clavipectoral fascia from above
  • 2nd part:
    
    • thoracoacromial vein
    • lateral throacic vein
  • 3rd part:
    
    • subscapular veins - run w subscapular artery and thoracodorsal nerve
    • anterior and posterior circumflex humeral veins
    • venae comitantes of forearm (brachial veins) ascend around the brachial artery and join axillary vein in a variable manner, w the medial one often joining basilic vein before it has become ax vein

Question 52

Anomalies and variations of aortic arch

Answer 52

• Commonest variation = for brachiocephalic artery and left common carotid artery to arise as a single and usually short common trunk
• Double aortic arch usu presents in childhood bc forms complete ring around oesophagus and trachea and causes obstructive symptoms early
  
  • V occasionally the anomaly is seen in the adult
• Right aortic arch is also an uncommon anomaly but can be present in the adult and is often assoc w situs inversus
  
  • In this situation left subclavian crosses behind oesophagus and other branches lie in front of trachea
  • Descending aorta then crosses to left side behind oesophagus
• Commonest anomaly of aortic arch – 1% = aberrant right subclavian artery arising from fourth part of aortic arch – this vessel usu passes posterior to oesophagus and can cause compressive symptoms (dysphagia lusoria)
  
  • Aberrant right subclavian artery often originates from a Kommerell’s diverticulum

Question 53

Structure of the breast

Answer 53

• breast = glandular epithelium, fibrous stroma and connective tissue surrounded by fat
  
  • also contains lymphocytes & macrophages
  • relative amount of each type of tissue varies according to age/life stage/pregnancy/breast feeding
• glandular epithelium forms complex branching ductal system that radiates outwards from nipple
  
  • each major duct has a dilated portion (lactiferous sinus) below the nipple-areolar complex - these ducts converge through a constricted orifice into ampulla of nipple​
  • 10-20 primary ducts, 30-40 segmental ducts and ~100 subsegmental ducts
  • each terminates in a lobular unit/terminal duct lobular unit that consists of clusters of ductules and acini
  • acini = milk forming glands of the lactating breast & together with their small efferent ducts or ductules are known as lobular units or lobules
  • terminal duct lobular units = invested in a specialised loose connective tissue that contains capillaries, lymphocytes & other migratory mononuclear cells (intralobular stroma - which is denser and more cellular from interlobular stroma and adipose tissue within breast)
• entire ductal system = lined by epithelial cells, which are surrounded by specialised myoepithelial cells which have contractile properties & serve to propel milk formed in lobules towrds the nipple
• breast epithelium is made up of 3 different cell types with distinct morphological features
  
  • superficial luminal A cells (dark nuclei, thought to be responsible for milk production)
  • basal (B) cells (large clear nuclei w distinctive intracellular filaments, most common type of cell)
  • myoepithelial cells (most abundant during lactation)
• together these cells form a bilayered configuration (outer myoepithelial and inner luminal) which is surrounded by a thick BM - separates breast epithelium from blood & lymphatics which lie within stroma
• NB typical breast cancers = malignant proliferations of epithelial cells; non-epithelial tumours of teh breast include sarcomas, lymphomas & phyllodes tumours

Question 54

Muscles of anteiror compartment of arm

Answer 54

• Supplied by musculocutaneous nerve (C5,6)
• Coracobrachialis
• Biceps
• Brachialis
• (+medial and lateral intermuscular septum)

Question 55

Muscles of posterior compartment of arm

Answer 55

• Triceps
  
  • long head from infraglenoid tubercle at upper end of ax border of scapula
  • lateral head has linear origin from back of humerus, above groove for radial nerve
  • medial head from whole back of humerus below radial groove
• supplied by radial nerve

Question 56

Muscles of anterior compartment of forearm

Answer 56

• superficial - 5, cross elbow joint
  
  • common origin from nt surface medial epicondyle; 3 have additional areas of origin
  • heel of hand on opposite medial epicondyle, 5 digits = 5 superficial muscles - thumb pronator teres, index FCR, middle FDS, ring PL, pinky FCU
  • all median nerve except FCU ulnar
• deep - 3, don’t cross elbow joint
  
  • FDP - anterior interosseous branch of median nerve & ulnar nerve
  • FPL - ant interosseous branch of median nerve
  • PQ - ant interosseous branch of median nerve

Question 57

muscles of posterior compartment of forearm

Answer 57

• 12 muscles
  
  • upper part = aconeus (superficial) & supinator (deep)
  • lateral part of humerus:
    
    • 3 muscles that pass along radial side = brachioradialis, ECRL, ECRB
    • 3 muscles that pass along posterior surface of forearm = ED, EDM, ECU
  • Forearm:
    
    • 3 muscles that emerge from deeply in between the above two groups and go to the thumb: abductor pollicis longus, EPL and EPB
    • Extensor indicis runs deeply to reach back of hand

Question 58

Anatomical snuffbox

Answer 58

• ulnar side: EPL tendon
• radial side: EPB & APL
• cutaneous branches of radial nerve cross these tendons
• cephalic vein begins in root of snuffbox from radial side of dorsal venous network
• radial artery, deep to all 3 tendons, lies on floor
• bony points palpable in snuffbox from prox to distal: radial styloid, scaphlid, trapezium, base of thumb metacarpal

Question 59

Thoracic sympathetic trunk*

Answer 59

The thoracic sympathetic trunk is part of the sympthatic nervous system outflow tract (T1-L2).

The ganglia reside anterior to the heads of the ribs. Sympathetic pre and post ganglionic fibres travels within the trunk to target organs.

Pre-ganglionic fibres may synapse within the ganglia at the same level, as is the case for vaso/pilo/sudomotor innervation of the arm.

They may also synapse at a higher level as exemplified by the sympathetics to the head and neck. From the synapse these nerves hitch-hike on blood vessels.

SNS neurons may synapse at the ganglia and travel on their own “splanchnic” nerve to a target organ, as is the case for the cardiopulmonary splanchnic nerves, as well as the great, lesser, and least splanchinic nerves of the lower thoracic trunk.

Question 60

Abdominal aorta*

Answer 60

The abdominal aorta commences at the level of T12 when the thoracic aorta passes through the median arcuate ligament. It descends to the level of L4 anterior to the vertebral bodies just to the left of the midline where it divides into a left and right common iliac artery. It also gives off a median sacral artery in the midline.

Immediate relations of the aorta are the left sympathetic trunk on its left side and the IVC on its right side. Between the SMA and IMA the uncinate process of the pancreas and third part of the duodenum pass anteriorly as well as the left renal vein. The coeliac, superior, and inferior mesenteric plexuses (SNS) lie on the aorta’s anterior surface. The hypogastric nerves pass over the common iliacs as they pass into the pelvis.

The aorta has 3 visceral branches; the Coeliac Axis at T12, the SMA at L1, and the IMA at L3. It has 3 paired branches to viscera; the adrenal arteries, the renal arteries at L2, and the gonadal arteries. Finally, the aorta has paired branches to the body wall; the inferior phrenic arteries and the 4 paired lumbar arteries.

Question 61

Bile ducts

Answer 61

• right hepatic duct formed by junction of right lateral (posteiror) and medial (anterior) ducts; right lateral curves round behind right medial duct (and other right medial sheath structures) - Hjortsjo’s crook - to join left side of right medial duct
  
  • this crook places right lateral sector bile duct at risk when right medial sector sheath is divided e.g. in extended left hepatectomy
  • RPSD has almost horizontal course, vs RASD more vertical
• in 30% of cases, some of segments of right side drain into main left hepatic duct - usu right lateral duct, but occasionally right medial duct
  
  • as they usu drain into left hepatic duct near confluence, if doing left hepatectomy should tie left hepatic duct as far to left as possible to avoid occluding right segments
• left sided bile duct can also drain into right hepatic duct
  
  • as right main sheath often quite short, damage to an aberrant left duct is best avoided by dividing right lateral and right medial sheaths separately, if possible, rather than main right sheath itself
• caudate lobe is drained by several ducts joining both ducts
• hepatic ducts formed by confluence of intrahepatic ducts exit from liver in a common sheath together w the branches of the portal vein and hepatic artery (as the portal triads)
• RHD
  
  • only terminal part is accessible surgically, outside liver parenchyma - has a short extrahepatic length before joining LHD
• LHD
  
  • has quite a long course at base of quadrate lobe surrounded only by fibrous tissue of Glisson’s sheath (hilar plate)
  • exposed by dividing peritoneum at base of quadrate lobe and opening hilar plate - allows LHD and portal vein to be delivered from hilum
  • LHD usu highest of the three strucutres nad lies above the left branch of portal vein
  • as it is traced to left, enters umbo fissure of liver at upper end of which the ligamentum teres terminates
  • tributaries from segments II, III and IV join LHD within or at base of umbilical fissure
• two major hepatic ducts are confluent to form the CHD, which changes its name to CBD at point of entry of cystic duct
• extrahepatic bile duct runs down anterior to PV and to right of HA in free edge of lesser omentum
  
  • supraduodenal artery crosses transversely anterior to duct immediately above duo
  • CBD passes behind D1 to right of GDA, and behind or in pancreas
  • at its lower end, curves to right where it isjoined by panc duct and enters D2 at ampulla of Vater
  • average length of CBD variable mainly bc of entry of cystic duct
  • av outer diameter 6-9mm, tendency for a greater diameter in older pts
  • blood supply
    
    • cystic artery above and posterior superior pancreaticoduodenal artery below
    • occasionally supply to lower bile duct is from GDA or hepatic artery itself
    • arteiral supply forms a plexus around duct
• innervation of biliary system
  
  • from celiac plexus - contains efferent, sympathetic and parasympathetic fibres and afferent fibres which run with the sympathetic afferents
• lymphatic drainage of bile ducts
  
  • upper ducts drain into nodes at hilum of liver around hepatic artery
  • lower part of duct drains into nodes along hepatic artery & also along superior pancreaticoduodenal nodes and behind pancreas into retroduodenal nodes
  • all these nodes drain back towards celiac axis

Question 62

Aberrant biliary anatomy

Answer 62

• normally RHD is divided into a right anterior and right posteiror branch which join to form a short right bile duct which joins w left to form a CHD outside the liver within the hilar plate in 60% of cases, and usu within 2cm of exit of RHD from liver
• variations in 40%
  
  • right anterior and posterior sectoral ducts entering separately into LHD/CHD/CBD
  • most common variations relate to RPSD which may drain into
    
    • LHD - 15% (RPSD independent of RASD and may curve posteriorly to RASD and join LHD some distance proximal to confluence - source of operative confusion & may lead to biliary injury or biliary fistula during liver resections)
    • directly into CHD - 10% (low down at an acute angle and almost at the point of entry of cystic duct; cystic duct may enter RPSD at this point)
    • trifurcation w RASD and LHD 11%
  • anatomy of left hepatic duct more constant
    
    • but in 3% segments II, III or IV ducts enter confluence separately
• aberrant hepatic duct = defined as a duct draining a normal portion of liver that joins the biliary tree outside of the liver

Question 63

Subclavian arteries

Answer 63

• on right originates from brachiocephalic trunk from aortic arch (rarely has its own origin off aorta as a lusorian artery, distal to left subclavian)
• on left is the posterior-most branch of aortic arch
• surface marking = along a line arching upwards from SCJ to middle of clavicle and ~2cm above it
• divided into 3 parts based on scalenus anterior
• first part = medial to scalenus anterior
  
  • vertebral artery (superior)
  • internal thoracic/mammary artery (inferior)
  • thyrocervical trunk (superior distal to vertebral artery); branches into
    
    • suprascapular artery
    • inferior thyroid artery
    • transverse cervical artery (becomes superficial cervical)
    • continues as ascending cervical artery
• second part = posterior to scalenus anterior
  
  • costocervical trunk - passes back across suprapleural membrane towards neck of first rib, and there divides into
    
    • superior intercostal artery which descends and enters thorax across neck of first rib
    • deep cervical artery which passes backwards between transverse process of C7 vertebra and neck of first rib to run upwards behind cervical transverse processes
• third part = lateral to scalenus anterior, lies behind prevertebral fascia on floor of posterior triangle
  
  • dorsal scapular artery - runs laterally through brachial plexus in front of scalenus medius then deep to levator scapulae to take part in scapular anastomosis
• relations
  
  • anteriorly:
    
    • scalenus anterior
    • vagus; recurrent laryngeal nerve recurs under right subclavian artery
    • thoracic duct loops over left artery
    • a connecting loop between middle and inferior cervical ganglia passes in front of subclavian artery and turns up behind it, forming ansa cervicalis
    • phrenic nerve passes down vertically across scalenus anterior, leaves medial border of muscle low down & crosses in front of subclavian artery & its internal thoracic branch, behind subclavian vein
  • posteriorly:
    
    • scalenus medius
  • inferiorly:
    
    • suprapleural membrane
    • passes over first rib to become axillary artery

Question 64

Sublavian vein

Answer 64

• anterior to scalenus anterior
• lies in a groove on first rib and due to slope of rib lies at a lower level than insertion of scalenus anterior
• runs medially & joins IJV at medial border of scalenus anterior to form the brachiocephalic vein; the thoracic duct on left and right lymph duct on right enter the angle of confluence of the two veins
• catheterisation
  
  • usual approach = infraclavicular, from a point 2cm below midpoint of clavicle along a line that passes behind clavicle towards jugular notch of sternum
  • needle pierces clavipectoral fascia and enters vein just behind fascia
  • complications: pneumothorax and subclavian artery puncture

Question 65

External iliac arteries

Answer 65

• commence in front of SI joints and course along pelvic brim on psoas major to pass deep to midpoint of ing lig, slightly below and lateral to mid-inguinal point, which is surface marking of deep inguinal ring
• initially tend to lie on ext iliac vein but by the time the ing lig is reached, vein is a direct medial relation
• anteriorly
  
  • ureters cross at ~origins of EIAs
  • genitofemoral nerves
  • in female, gonadal vessels cross in front, distal to ureteric crossing
  • in male, gonadal vessels lie in front on their way to the int inguinal ring and ductus deferens crosses in front of vessels also
• each EIA gives two moderate-sized branches just before it exits into thigh
  
  • inf epigastric artery arises from EIA’s anterior surface and passes forwards medial to int inguinal ring
  • deep circumflex iliac artery arises from EIA’s lateral side and passes deeply along ing ligament towards ASIS
    
    • these vessels are accessible by dissecting the CFA

Question 66

Internal iliac arteries

Answer 66

• usu 2-4cm long, pass downwards and posteriorly towards greater sciatic foramen where they divide into an ant and post trunk
• each artery lies anterior to its corresponding vein and behind the ureter (and ovary in female)
• obturator nerve lies on the pelvic wall lateral to it
• although the usual origin of obturator artery is anterior trunk of int iliac artery, in ~20% cases it arises from the inf epigastric artery
  
  • this then passes variably in relation to the femoral ring, prob most often in front of the ring
• branches
  
  • posterior division:
    
    • iliolumbar artery
    • lateral sacral artery
    • superior gluteal artery
  • anterior division
    
    • 3 vesical branches:
      
      • superior vesical (persistent part of umbilical artery)
      • inferior vesical
      • obliterated umbilical (continuation of superior vesical)
    • 3 visceral branches
      
      • uterine artery
      • vaginal artery
      • middle rectal artery
    • 3 parietal branches
      
      • obturator artery
      • pudendal artery
      • inferior gluteal artery

Question 67

Calot’s triangle and hepatocystic triangle

Answer 67

Calot’s triangle

• Calot described cystic artery, cystic duct and CHD
• Hepatocystic triangle = upside-down triangle
  
  • base = undersurface of liver
  • the two sides the cystic duct (and GB) and CHD
  • apex the junction between the two
  • more useful as it is formed by and contains the most important structures related to cholecystectomy
  • in particular the RHA and its variations nearly always cross through the floor of this triangle & cystic artery crosses also

Question 68

Greater omentum*

Answer 68

Greater omentum

Question 69

Thigh muscles

Answer 69

• 3 muscle compartments, enclosed by deep fascia of thigh - fascia lata
• fascia lata = thickest laterally where it forms iliotibial tract
  
  • fascia lata gives off two septa which separate muscles of thigh into two compartments
  • lateral intermuscular septum = thicker than medial intermuscular septum; both septa insert into linea aspera of femur
• psoas major and iliacus muscles (L1-3) - iliopsoas
  
  • psoas major arises from T12-L5 and transverse processes of L1-5 and passes downwards along pelvic brim, behind middle of ing ligament and in front of capsule of hip joint to insert into lesser trochanter
    
    • lumbar spinal nerves L1-3
  • iliacus arising from inside pelvis has tendon which blends w that of psoas major at its insertion into lesser trochanter
    
    • femoral nerve
• sartorius (S2-4)
  
  • arises from ASIS and the bone immediately subjacent; crosses thihg obliquely and inserted via a flat tendon into medial surface of tibia
    
    • femoral nerve
• quadriceps compartment muscles (branches of femoral nerve)
  
  • rectus femoris - from ileum
    
    • arises by 2 tendons, one from ASIS and other above acetabulum
    • its superficial fibres are bipennate and it inserts via patellar tendon
  • vastus group - from femur and all insert via patellar tendon
    
    • vastus lateralis = largest
      
      • arises from broad aponeurosis from front of femur below greater trochanter then origin spirals around shaft laterally and down to prox half of linea aspera
    • vastus medialis
      
      • also from front of femur below lesser trochanter
      • origin spirals around shaft medially and downwards to involve all of linea aspera and the prox part of the medial supracondylar line
      • also takes origin from adductor longus and magnus and the medial intermuscular septum
      • lowermost fibres are horizontal and give the rounded bulge above the knee joint
    • vastus intermedius
      
      • arises from prox 2/3 of ant and lateral surface of femur
      • deepest of muscles to insert via patellar tendon
    • patellar tendon = strong tendon through which all of the quads muscles insert into base of patella
    • ligamentum patellae inserts into tibial tuberosity
• adductor compartment muscles
  
  • ​gracilis (obturator nerve)
    
    • most superficial
    • arises from lower part of pubic body and ramus and ischial ramus,–> curves around medial femoral condyle as a flat tendon which inserts into upper tibia immediately behind Sartorius insertion
    • overlies adductor magnus
    • hip flexor and adductor
  • pectineus (L2,3 - femoral nerve +/- obturator)
    
    • flat, quadrangular muscle which arises from pectin pubis and adjacent bone, passes obliquely to insert into femur between lesser trochanter and linea aspera
    • hip adductor
  • adductor longus (L2,3 - anterior division of obturator)
    
    • arises from front of pubis between medial end of origin of pectineus and upper end of origin of gracilis
    • most anterior of the adductor muscles in the thigh and fans out from its origin to insert into linea aspera in middle third of femur
    • lies between vastus medialis anteriorly and adductor magnus posteriorly; between adductor longus and vastus medialis = medial intermuscular septum
      
      • all 4 structures are blended near femur & no plane of separation between them
    • forms floor/posterior wall of adductor canal
  • adductor brevis
    
    • arises from pubis immediately deep to gracilis –> inserts into femur in a line from lesser trochanter to linea aspera, again immediately deep to gracilis
    • may be partly fused w adductor magnus
    • profunda femoris vessels lie in front of it, as does ant branch of obturator nerve which supplies it
    • post branch of obturator nerve posterior to it
  • adductor magnus (obturator nerve, except for part arising from ischial tuberosity which is supplied by sciatic nerve)
    
    • largest & most posterior of adductors
    • arises from inf pubic ramus, ischial pubic ramus and ischial tuberosity
    • pubic fibres pass almost horizontally into lower part of gluteal tuberosity (adductor minimus) and then descending fibres inserted into linea aspera
    • fibres from ischial tuberosity insert as a tendon into adductor tubercle of medial femoral condyle
    • anterior to muscle = profunda femoris vessels below adductor brevis
    • posterior to adductor magnus = sciatic nerve and hamstring group of muscles
    • the muscle has tendinous arches in its insertion; prox four of these have perforating arteries from profunda femoris artery passing through them
• posterior femoral compartment muscles - hamstrings
  
  • span the hiph and knee joint, extending the hip & flexing the knee
  • biceps femoris - arises by two heads
    
    • long head = from inferior aspect of ischial tuberosity (in common w origin of ST)
      
      • supplied by tibial component of sciatic nerve
    • short head = from linea aspera and lateral supracondylar line between insertion of adductor magnus and origin of vastus lateralis; also arises from lateral intermuscular septum
      
      • supplied by common peroneal component of sciatic nerve
    • belly lies posterior to sciatic nerve
    • inserts via a tendon which splits around fibular collateral ligament and attaches to head of fibula
    • common peroneal nerve lies immediately medial to tendon of biceps, between it and lateral head of gastroc
  • semitendinosus (tibial part of sciatic nerve)
    
    • arises from ischial tuberosity with long head of biceps
    • muscle belly ends about halfway down thigh; gives way to a tendon which runs down on muscle belly of SM then curves round medial femoral condyle to insert into tibia immediately behind insertion of sartorius and fused w that of gracilis
  • semimembranosus (tibial part of sciatic nerve)
    
    • attached to ischial tuberosity in front of biceps/ST origin and also arises from an aponeurosis associated w these muscles
    • insertion also somewhat complex, giving a strong slip of insertion into posterior and lateral aspect of medial tibial condyle and other slips passing in various directions from this insertion and blending w capsule of knee joint
    • in lower part of course, muscle belly overlies (is posterior to) popliteal vessels

Question 70

Leg muscles

Answer 70

Leg muscles

Question 71

Leg arteries

Answer 71

• femoral artery starts behind midpoint of ing ligament w vein medial
• transversalis and iliopsoas fasciae condense to form a sheath around femoral vessels (femoral sheath) which extends beneath ing lig; medial to femoral sheath is femoral canal
• fem vessels descend from anterior to posterior on medial side of thigh, running through adductor muscles of thigh
  
  • in mid-thigh, femoral vein lies posteriorly to artery
• branches of fem artery
  
  • superficial epigastric artery - arises in vicinity of ing lig and passes ant and superficial to ing lig
  • superficial circumflex iliac artery - arises at about same level as SEA and passes laterally towards ASIS, approx 1cm below ing ligament (often the supply on which a groin flap is based)
  • superficial external pudendal artery - arises from medial side of prox femoral artery & may cross superficial or deep to GSV
  • deep external pudendal artery - arises from medial side and crosses in front of femoral vein but behind GSV to medial thigh; often absent
  • profunda femoris - arises posterolaterally from femoral artery and spirals behind femoral artery and vein as it passes downwards, lying on adductor longus
    
    • soon after its origin, gives off medial and lateral circumflex arteries; these not uncommonly arise directly from fem artery itself
    • lateral circumflex femoral artery runs between branches of femoral nerve
• profunda femoris artery (and vein) in thigh lie posterolaterally to their femoral counterparts at their origin then pass downwards towards medial surface of femur
  
  • profunda femoris vein or a branch of it lies behind SFA, separating it from its own profunda femoris (deep femoral) artery branch
  • lie deep to adductor longus (which therefore separates them from the femoral vessels) on adductor brevis and then adductor magnus and terminate as fourth perforating vessels
  • give off muscular branches, including first to third perforating vessels, which traverse the tendinous arches in adductor magnus

Question 72

Upper arm muscles

Answer 72

Upper arm muscles

Question 73

Forearm muscles

Answer 73

Forearm muscles

Question 74

Popliteal fossa

Answer 74

• diamond shaped area found at posterior aspect of knee
• main path by which structures move from thigh to leg
• borders
  
  • superomedial: semimembranosis
  • superolateral: biceps femoris
  • inferomedial: medial head of gastrocnemius
  • inferolateral: lateral head of gastrocnemius and plantaris
  • floor = posterior surface of knee joint capsule & posterior surface of femur
  • roof = 2 layers: popliteal fascia and skin
    
    • popliteal fascia = continuous w fascia lata of leg
• contents:
  
  • from medial to lateral:
    
    • popliteal artery
    • popliteal vein
    • tibial nerve
    • common fibular nerve
  • tibial and common fibular nerves = most superficial of the contents of the popliteal fossa
    
    • both = branches of sciatic nerve
    • common fibular nerve follows biceps femoris tendon, running along lateral margin of popliteal fossa; branches are:
      
      • sural communicating nerve (pierces roof of fossa to join sural nerve)
      • lateral cutaneous nerve of calf (pierces roof of fossa over lateral head of gastrocnemius)
      • genicular nerves
    • tibial nerve (runs vertically down through middle of pop fossa to pass between heads of gastroc); branches are:
      
      • sural nerve (runs between 2 heads of gastroc)
      • three genicular nerves
      • motor branches to muscles in popliteal fossa
  • small saphenous vein pierces popliteal fascia of popliteal fossa to enter the diamond and empty into popliteal vein
  • popliteal artery = deepest structure in popliteal fossa
    
    • is a continuation of the femoral artery, and travels in leg to supply it w blood
    • branches are 5 genicular arteries:
      
      • superior and inferior medial
      • superior and inferior lateral
      • middle
    • beyond the fossa, branches into anteiror tibial, fibular and posterior tibial arteries

Question 75

Femoral nerve*

Answer 75

The femoral nerve is formed in the lumbar plexus from the posterior divisions of spinal nerves L2 L3 and L4.

It passes through the substance of psoas major (supplies it and iliacus) and exits between iliacus and psoas to pass under the inguinal ligament. It is under the ilopsoas fascia and so is separate from the femoral sheath.

Once inside the femoral triangle it divides early into many branches to supply pectineus, sartorius, medial and intermediate femoral cutaneous nerves, quadriceps, and finally the saphenous nerve, which exits the triangle and passes between sartorius and gracilis.

Question 76

Tibial nerve*

Answer 76

The sciatic nerve divides into tibial and peroneal components at the apex of the popliteal fossa.

The tibial nerve drops down between the heads of gastrocnemius, behind the knee joint, and deep to the soleal arch. In the popliteal fossa it supplies the knee joint and gives off the sural nerve.

From the fibrous arch of the soleus, the tibial nerve runs down with the posterior tibial vessels between FHL and FDL. It supplies the soleus, TP, FHL and FDL. The tibial nerve passes behind the medial malleolus and divides into the medial and lateral plantar nerves.

Question 77

Peroneal nerve*

Answer 77

Peroneal nerve

Question 78

Femoral vein

Answer 78

• begins where popliteal vein ends
• ascends with artery in medial thigh from posterior to anterior; in mid thigh lies posterior to artery
• ends just medial to femoral artery which is behind midpoint of inguinal ligament
• two main tributaries in femoral region are GSV anteirorly and profunda femoris vein posteirorly
  
  • profunda femoris vein tends to lie between femoral and profunda femoris arteries, and therefore is at risk when these arteries are being mobilised
  • circumflex femoral veins variable in their pattern of drainage but more often drain directly into femoral vein
  • cutaneous veins corresponding to the branches from the femoral artery tend to drain into the GSV rather than directly into femoral vein, though there is considerable variability

Question 79

Sciatic nerve*

Answer 79

The sciatic nerve is formed at the inferior border of the piriformis muscle by the confluence of its tibial and peroneal components (L4, L5, S1, S2, S3).

It passes into the buttock below piriformis at the midpoint between the ischial tuberosity and greater trochanter and descends in the hamstring compartment.

The sciatic nerve supplies all the hamstring muscles and the ischial fibres of adductor magnus. At the apex of the popliteal fossa it splits into tibial and common peroneal nerves.

Question 80

Subsartorial canal

Answer 80

• a gutter-shaped groove that runs below the Sartorius muscle in the thigh
• serves as a passageway for structures moving between anterior thigh and posterior leg - runs from apex of femoral triangle to adductor hiatus (a gap between the adductor and hamstring attachments of adductor magnus)
• bounded
  
  • laterally: vastus medialis
  • posteriorly: adductor longus above, adductor magnus below
  • medially: sartorius (separated from vessels by a strong fascial layer which joins the medial intermuscular septum)
• contents include
  
  • femoral artery and vein
  • long saphenous nerve lying anterior to artery
  • further medially in upper part, the nerve to vastus medialis before it penetrates VM
• femoral artery always between vein and saphenous nerve; femoral vein spirals from medial to artery in femoral triangle to posterior to artery in canal
  
  • femoral artery exits by passing through adductor hiatus of adductor magnus into the popliteal fossa; at this point the vein is posterolateral to the artery
  • branches from artery in the thigh are muscular only and usu small in health but can enlarge considerably if supplying a tumour
• saphenous nerve exits canal between sartorius and gracilis and runs down leg behind GSV
• original surgical relevance was rapid access to great vessels of leg for swift amputation
• distal aspect of canal is accessed for modern supra-genicular approaches to popliteal artery
  
  • saphenous nerve must be preserved during this procedure

Question 81

Median nerve

Answer 81

• terminal branch of brachial plexus, takes divisions from lateral and medial cords to derive supply from C5-T1
• ax artery clasped between the 2 roots, with median root crossing in front of vessel
• nerve starts lateral to ax artery, passes through arm anterior to it & at cubital fossa is medial to it
• descends between 2 heads of pronator teres and passes deep to fibrous arch of FDS
• emerges between FCR & PL before entering carpal tunnel
• gives vasc (sympathetic) branches to brachial artery & may give branch to PT above elbow joint
• around elbow joint gives branches to FCR, FDS (but nerve to index finger part of this arises in middle of forearm) and PL
• supplies elbow & prox radioulnar joints
• deep to FDS, gives off ant interosseous branch which supplies FDP (bellies that move index and middle fingers), FPL, PQ and inferior radioulnar, wrist and carpal joints
• in distal forearm, above FR, gives off palmar branch to skin over thenar muscles; pierces deep fascia just above flexor retinaculum
• in carpal tunnel divides into medial and lateral branches
  
  • lateral gives off muscular recurrent branch (T1) which supplies radial 2 lumbricals and thenar muscles - LOAF (lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis)
  • medial branch divides into 2 palmar digital nerves - supply flexor skin of radial 3.5 digits and nail beds and dorsal skin over distal & middle phalanges of these digits (but only autonomous area of median nerve supply are over the pulp pads of 2nd and 3rd digits)
• injury at wrist/carpal tunnel:
  
  • loss of sensation over pulp pads of index and middle fingers
  • can’t abduct thumb –> in longstanding cases, thenar eminence wasting
• proximal to midforearm
  
  • wasting of front of forearm bc long flexors (except FCU and half of FDP) paralysed
  • pronators paralysed
  • hand held with index finger straight in ‘pointing finger’ position, often w all other fingers flexed incl middle finger (though part of FDP to middle finger tendon usu has a median supply, its close connection w the part supplied by ulnar nerve can lead to middle finger flexion)
    
    • branch to index finger part of FDS arises near mid-forearm rather than in cubital fossa

Question 82

Radial nerve

Answer 82

• origin: C5-T1 posterior cord of brachial plexus
• direct continuation of post cord, passes beyond posterior wall of axilla, below tendon of lat dorsi (via lateral triangular space)
• spirals across back of humerus, between lateral and medial heads of triceps, lying on radial groove of bone, deep to lateral head
• pierces lateral intermuscular septum 1/3 of the way down from the deltoid tuberosity to the lateral epicondyle
• in extensor compartment of lower arm it descends in the intermuscular slit between brachialis and brachioradialis, to lie lateral to to antecubital fossa
• supplies
  
  • posterior cutaneous nerves of arm & forearm, lower lateral cutaneous nerve of arm
  • muscular branches to triceps, brachioradialis, ECRL, aoneus and small twig to brachialis
• posterior interosseous comes off radial under brachioradialis, passes between 2 heads of supinator and into extensor compartment - lies on APL then interosseous membrane
  
  • supplies all muscles in extensor compartment of forearm (except those supplied by radial nerve above)
  • sensory to deep structures but no cutaneous branches
• after giving off posterior interosseous branch, the rather slender remnant (purely cutaneous now) becomes superficial branch of radius
  
  • lies under brachioradialis, over supinator, PT & FDS
  • passes lateral/posterior to brachioradilais, lateral to radial artery, posterior to radial styloid then tendon of EPL as it forms the dorsal side fo snuff box
  • several terminal branches to skin of back of hand & 3.5 fingers short of nail beds
• sensory supply: posterior arm and forearm, lateral 2/3 of dorsum of hand and proximal dorsal aspect of lateral 3.5 fingers
• motor supply: posterior compartment of arm - triceps, and posterior compartment of forearm (brachiordialis, aconeus, supinator, ECRL and ECRB, ECU, ED, EPL and EPLB, EI, EDM, abductor pollicis longus
• injuries
  
  • most commonly high from fractures of shaft of humerus, also transient paralysis from crutch pressing on nerve in axilla or Saturday night palsy
    
    • wrist drop - unable to extend wrist and MCPJs (but IPJs can still be straightened by action of interossei and lumbricals)
    • minimal sensory loss usu just over first dorsal interosseous
  • with high injuries in axilla - triceps paralysis so weak elbow extension (this doesn’t occur after humeral shaft fracture)

Question 83

Ulnar nerve

Answer 83

• terminal nerve of medial cord
• runs down between axillary artery & vein behind medial cutaneous nerve of forearm
• continues downwards & backwards posterior to brachial vessels to pierce medial intermuscular septum
• then descends along triceps by lying on shaft of humerus between medial epicondyle & olecranon
  
  • susceptible to injury in supracondylar fractures and elbow dislocations
• enters forearm from extensor compartment by passing between humeral and ulnar heads of FCU
• in forearm descends on FDP under cover of FCU; here is joined by ulnar artery
• the 2 emerge from beneath tendon of FCU, passing distally over flexor retinaculum alongside the pisiform bone, where it divides into superficial and deep branches
• supplies
  
  • has no branches in upper arm but gives a branch to elbow joint & a motor branch to supply FCU and the ulnar half of FDP
  • superficial branch: skin of ulnar 1.5 digits
    
    • dorsal branch supplies dorsal aspect
    • palmar branch supplies palm of ventral aspect
    • superficial branch supplies digits of ventral aspect
  • deep branch: intrinsic muscles of hand are concerned w fine movement
    
    • adductor pollicis
    • all dorsal and palmar interossei
    • 3rd & 4th lumbricals
    • abductor/opponens/flexor digiti minimi
• injuries - “the closer to the paw, the worse the claw”
  
  • most commonly injured below elbow or at wrist
    
    • can be compressed in cubital tunnel formed by tendinous arch connecting humeral and ulnar heads of FCU - may require division of aponeurotic ulnar origin of muscle & ant submuscular transposition of nerve
    • at wrist:
  • low lesions (below elbow):
    
    • more marked clawing as FDP to ring and little fingers still functions
    • hyperextension of MCPJs of ring & little fingers and flexion of IPJs bc their interossei and lumbricals are paralysed so can’t flex MCPJs or extend IPJs
    • claw produced by unopposed action of finger extensors and FDP
  • high lesions (at or above elbow)
    
    • paralysis of FDP to ring and little fingers leads to less marked clawing of these fingers bc flexion component of clawing is less prominent - known as ulnar paradox
    • variable sensory loss on ulnar side of hand and on little & ring fingers but often less than expected
    • otherwise as for low lesion, guttering between metacarpals

Question 84

Obturator nerve

Answer 84

Obturator nerve