Anatomy

Question 1

Adrenal Glands

Answer 1

• Paired endocrine glands situated over the medial aspect of the upper poles of each kidney
• Posterior abdomen, retroperitoneal (parietal peritoneum covers anterior surface only)
• Right - pyramidal shape
• Left - semi-lunar shape
• Separated from the kidneys by the perirenal fat, enclosed in perinephric fascia
• Secrete steroid and catecholamine hormones directly into the blood

Relations
* Right gland anterior - IVC, right lobe of liver
* Right gland posterior - right crus of the diaphragm
* Left gland anterior - stomach, pancreas, spleen
* Left gland posterior - left crus of the diaphragm

Structure
* Outer connective tissue capsule
* Cortex
– Zona glomerulosa - aldosterone
– Zona fasciculata - cortisol + small amount of androgens
– Zona reticularis - androgens + small amount of corticosteroids
* Medulla - contains chromaffin cells which secrete catecholamines
* Veins and lymphatics leave each gland via the hilum
* Arteries and nerves enter the glands at numerous sites

Vasculature
* Superior adrenal artery - inferior phrenic
* Middle adrenal artery - abdominal aorta
* Inferior adrenal artery - renal arteries
* Right adrenal vein –> IVC
* Left adrenal vein –> left renal vein

Innervation
* Coeliac plexus
* Greater splanchnic nerves
* Sympathetic innervation - myelinates pre-synaptic fibres T10-L1

Lymphatics
* Lumbar lymph nodes by adrenal lymphatic vessels
* 2 lymphatic plexuses - one deep to the capsule, one in the medulla

Question 2

The nasopharynx

Answer 2

• Uppermost region of the pharynx
• Muscular box shaped passageway extending from behind the nose to just above the roof of the mouth
• Directly behind the posterior nasal apertures and superior to the level of the soft palate
• Roof and posterior wall - mucosa overlying the base of the skull (sphenoid bone, basal part of occipital bone)
• Posterior extension of the nasal cavity - permits free passage between it and the nasal cavities
• Rigid roof, posterior and lateral walls create a vaulted space that is always open
• Posterolateral walls bear the openings of the auditory tubes (Eustachian) - lie above the level of the hard palate and connect the nasopharynx to the middle ear cavity
• Opens into the cavity of the oropharynx through the pharyngeal isthmus (lies between posterior border of the soft palate and the posterior pharyngeal wall)
• Contains adenoids (nasopharyngeal tonsils) in the roof (large collection of lymphoid tissue)
• Lined with respiratory epithelium; ciliated pseudostratified columnar epithelium with goblet cells

Functions
* connects the nasal cavity to the larynx and trachea via the oropharynx
* voice resonance and production
* equalization of air pressure between the middle ear and the atmosphere
* immune protection against infections

Question 3

Ankle block

Answer 3

Indications
* all types of foot surgery
* diagnostic and therapeutic purposes
* analgesia for fractures, sort tissue injuries and gout

Contraindications
* local infection
* soft tissue trauma
* distorted anatomy with scarring in the area of block placement

5 Peripheral Nerves
* Saphenous nerve (femoral L3-4) - medial aspect of foot
* Sural nerve (tibial/superificial peroneal –> sciatic L5-S2) - lateral aspect of foot
* Tibial nerve (tibial –> sciatic L5-S3) - deep structures and sole of foot –> lateral and medial plantar nerves, calcaneal nerve
* Superficial peroneal nerve (common peroneal –> sciatic L4-S2) - dorsum of foot
* Deep peroneal nerve (common peroneal –> sciatic L4-S2) - deep dorsal structures and 1st web space

Performing the Block
* Prerequisites - consent, monitoring, IV access, trained assistant, equipment, emergency drugs
* Skin cleaning
* Prep-stop-block
* Position - supine with a pillow under the calf
* Total of 15-20ml of LA
* Saphenous (just anterior to medial malleolus), sural (posterior to medial malleolus) and superficial peroneal nerves (anterior ankle) are blocked with a circumferential s/c injection of 10-15ml along a line just proximal to the malleoli and anterior from the achilles tendon medially to laterally
* Deep peroneal - 5ml just lateral to extensor hallucis longus tendon, deep to the retinaculum along the same circumferential line, lateral to dorsalis pedis artery
* Posterior tibial - 5ml just posterior to the posterior tibial artery if palpable, or mid-way between the Achilles and medial malleolus deep to the retinaculum

Question 4

Antecubital fossa

Answer 4

• Triangular shaped depression over the anterior aspect of the elbow joint

Borders
* Lateral - medial border of the brachioradialis muscle
* Medial - lateral border of pronator teres
* Superior - horizontal line drawn between the epicondyles of the humerus
* Roof - bicipital aponeurosis, fascia, subcutanous fat and skin
* Floor - brachialis (proximally) and supinator (distally)
* Apex - meeting point of medial and lateral borders

Contents (lateral to medial)
* Radial nerve - divides into superifical and deep
* Biceps tendon - attaches radial tuberosity and gives rise to bicipital aponeurosis
* Brachial artery - bifurcates to radial and ulnar arteries at the apex
* Median nerve
* Roof contains median cubital vein

Question 5

Anterior triangle

Answer 5

• Region at the front of the neck

Borders
* Superior - inferior border of mandible
* Lateral - anterior border of SCM muscle
* Medial - sagittal line down the midline of the nexk
* Roof - investing fascia
* Floor - visceral fascia

Contents
* Muscles - 4x suprahyoids, 4x infrahyoids
* Nerves - CNs VII, IX, X, XI, XII
* Arteries - common carotid –> external and internal branches
* Veins - IJV
* Lymph nodes

Subdivisions
* Carotid triangle - common carotid, IJV, hypoglossal and vagus nerves
* Submental triangle - submental lymph nodes
* Submandibular triangle - submandibular salivary gland, lymph nodes, facial artery and vein
* Muscular triangle - infrahyoid muscles, pharynx, thyroid, parathyroids

Question 6

Arterial supply of the lower limb

Answer 6

• Aorta
• Common iliac arteries
• Common femoral artery (behind the inguinal ligament)
• Branch to deep femoral artery
• Superficial femoral artery
• Popliteal artery
  – anterior tibial –> dorsalis pedis
  – posterior tibial –> branch for peroneal artery
• Plantar arch

Question 7

Arterial supply of the upper limb

Answer 7

• Subclavian artery
• Axillary artery
• Brachial artery (divides at cubital fossa)
  – radial artery
  – ulnar artery
• Superficial and deep palmar arches

Question 8

Autonomic nervous system

Answer 8

A collection of nerves and ganglia that are involved in the involuntary control of homeostasis and the stress response.

Sympathetic nervous system
* Pre-ganglionic myelinated fibres, short cell bodies
* Pre-ganglionic neurotransmitter is acetylcholine, with nicontinic cholinergic receptors
* Sympathetic outflow tract is T1-L2
* Post-ganglionic unmyelinated fibres
* Postganglionic neurotransmitter are adrenergic and release noradrenaline
* Sweat glands are cholinergic with muscarinic ACh receptors
* Sympathetic organs/structures: sweat glands, most blood vessels, kidneys, adipose tissue, errector pili muscle

Parasympathetic nervous system
* Pre-ganglionic myelinated fibres, long cell bodies
* Pre-ganglionic neurotransmitter is Ach, with nicotinic cholinergic receptors
* Craniosacral outflow tract - CN III, VII, IX, X and S2-4
* Post-ganglionic unmyelinated fibres
* Postganglionic neurotransmitters are cholinergic with muscarinic acetylcholine receptors
* Parasympathetic organs/structures: lacrimal glands

Paravertebral sympathetic chain
* Superior cervical ganglion
* Middle cervical ganglion
* Inferior cervical ganglion
* Inferior ganglion fuses with the first thoracic ganglion to form the stellate ganglion
* Thoracic - series of ganglia from each thoracic segment
* T1-T5 branches supply the aortic, cardiac and pulmonary plexi
* Lumbar - anterior to the vertebral column as the pre-vertebral ganglia
* Branches from here form the coeliac plexus

Parasympathetic ganglia
* Ciliary ganglion
– from edinger-westphal nucleus –> oculomotor nerve –> ciliary ganglion –> short ciliary nerves –> sphincter pupillae, ciliary muscles
* Sphenopalatine/ptergyopalatine ganglion
– from superior salivatory nucleus –> greater petrosal nerve and nerve of pterygoid canal –> pterygopalatine ganglion –> maxillary nerve –> lacrimal gland, nasopharynx, palate, nasal cavity
* Submandibular ganglion
– superior salivatory nucleus –> chorda tympani (facial nerve) –> submandibular ganglion –> direct to sublingual and submandibular glands
* Otic ganglion
– inferior salivatory nucleus –> lesser petrosal nerve –> otic ganglion –> auriculotemporal nerve –> parotid gland
* Vagus nerve –> thorax and abdomen
* Sacral outflow (S2-S4) –> pelvic splanchnic nerves through the anterior roots of spinal nerves

Question 9

Blood supply to the brain

Answer 9

Arterial Blood Supply
- from the arch of the aorta - right brachiocephalic - divides to form right subclavian and right common carotid; left common carotid and left subclavian arise directly from the arch
- internal carotid arteries (originate at the bifurcation of the left and right common carotid arteries at C4)—> anterior and middle cerebral arteries
- ICAs move superiorly within the carotid sheath, enter the brain via the carotid canal of the temporal bone
- ICAs pass anteriorly through the cavernous sinus
- distal to the cavernous sinus, each ICA gives rise to ophthalmic artery, posterior communicating artery, anterior choroidal artery, ACA (anteromedial cerebrum) then continue as the MCA (lateral cerebrum)
- vertebral arteries - arise from subclavian arteries, medial to the anterior scalene muscle
- ascend the posterior aspect of the neck, through holes in the transverse processes of the cervical vertebrae (foramen transversarium)
- enter the cranial cavity via the foramen magnum
- give off meningeal branch (falx cerebelli), anterior and posterior spinal arteries (spinal cord), PICA (cerebellum)
- converge to form basilar artery —> branches to the cerebellum and pons
- bifurcates to form PCAs (medial and lateral posterior cerebrum)
- anastomotic circle (“Circle of Willis”)

Venous Drainage
- of the brain and meninges - supplied by the dural venous sinuses
- spaces between periosteal and meningeal layers of dura mater, lined by endothelial cells
- superior sagittal sinus —> confluence of sinuses
- inferior sagittal sinus + great cerebral vein —> straight sinus —> confluence of sinuses
- occipital sinus –> confluence of sinuses
- right transverse sinus –> confluence of sinuses
- confluence of sinuses –> left transverse sinus and sigmoid sinus —> IJV (superior and inferior pterosaurs veins also drain into transverse/sigmoid sinus)
- ophthalmic veins –> cavernous sinus –> petrosal vein –> sigmoid sinus
- of the scalp and face - drained by veins synonymous with the arteries of the face and scalp —> empty into the IJV/EJV
- of the neck - anterior jugular veins
- EJV - external face, formed by union of posterior auricular vein and retromandibular vein (posterior branch) - combine immediately posterior to the angle of mandible, and inferior to the outer ear
- AJV - drain anterior aspect of neck, communicating via jugular venous arch, descending down middle of neck, emptying into SCV
- IJV begins in cranial cavity as continuation of sigmoid sinus, exits via jugular foramen

Question 10

Spinal cord blood supply

Answer 10

3 longitudinal arteries
- anterior spinal artery (formed at the foramen magnum from the union of the vertebral arteries, travelling in the anterior median fissure) —> Sulcal arteries which enter the spinal cord –> supplies anterior two-thirds of the spinal cord
- 2 posterior spinal arteries (originate from the vertebral artery or the PICA, anastamosing with one another in the pia mater) –> supplies posterior one-third

Below cervical level, supply from longitudinal arteries is insufficient
- anastomosis of surface vessel branches from ASA and PSA –> pial arterial plexus, supplies outer portion of the spinal cord
- anterior and posterior segmental arteries are derived from spinal branches of a number of arteries, before entering the vertebral canal through the intervertebral foramina
- great anterior segmental artery of Adamkiewicz reinforces circulation to the inferior 2/3rds of the spin cord (found on the left in the majority of individuals) –> arises from the left side of the aorta, between T9 to L1 usually
- segmental and radicular arteries supply (and follow the path of) the anterior and posterior nerve roots
- formation of ‘watershed areas’ that are at risk of ischaemia (T3-5 and T12-L1)

Venous drainage
– radicular and spinal veins
– drain into internal vertebral venous plexus
– drain into azygous system and SVC
– plexus communicates with the basilar sinus in the brain, the pelvic veins and IVC

Question 11

Brachial plexus (and blocks)

Answer 11

Roots - anterior rami of C5-T1
–> pass between the anterior and medial scalene muscles to enter the base of the neck
– dorsal scapular and long thoracic nerves

Trunks
– superior (C5, C6)
– middle (C7)
– inferior (C8, T1)
–> travel laterally, crossing the posterior triangle of the neck
– suprascapular nerve and nerve to subclavius

Divisions - divide into anterior and posterior divisions
– 3 anterior nerve fibres
– 3 posterior nerve fibres
–> leave the posterior triangle and pass into the axilla, re-combining into cords

Cords - named by their position relative to the axillary artery
– lateral cord - anterior division of superior and middle trunks - gives off lateral pectoral nerve
– posterior cord - posterior divisions of superior, middle and inferior trunk - gives off superior and inferior subscapular nerves and throracodorsal nerve
– medial cord - anterior division of inferior trunk - gives off medial pectoral nerve, medial cutaneous nerve of arm and forearm

Branches
– musculocutaneous branch from lateral cord
– axillary branch from posterior cord
– median branch from lateral and medial cords
– radial branch from posterior cord
– ulnar branch from medial cord

Brachial Plexus Blocks
* Interscalene - surgery to shoulder and upper arm where roots become trunks (ulnar sparing, phrenic nerve blockade common with high volume)
* Supraclavicular - surgery to the midhumerus and more distally at the position where trunks become divisions (may be ulnar sparing)
* Infraclavicular - surgery to the arm and hand as the divisions become cords
* Axillary - surgery to the forearm and hand as the cords become branches (axillary nerve missed)
* (can supplement with individual nerve blocks in upper arm/forearm)
* intercostobrachial nerve on inside of upper arm (usually T2)

Performing the Blocks
* Prerequisites - consent, monitoring, IV access, trained assistant, equipment, emergency drugs
* Skin cleaning
* Prep-stop-block
* Interscalene
– Position - head rotated to contralateral side, pillow behind head but not shoulder
– Total of 7-15ml of LA
– Traffic light appearance of cross-sectional view with probe transverse on the neck, 3-4cm superior to the clavicle
* Supraclavicular
– Position - head rotated to contralateral side, pillow behind head but not shoulder, arm adducted
– Total of 20-25ml of LA
– Brachial plexus - cluster of hypoechoic round or ovoid structures posterior and superior to the subclavian artery with probe transverse on the neck, superior to the clavicle at the midpoint
* Infraclavicular (superior border - clavicle, lateral - deltopectoral groove, inferior - upper margin of pec major)
– Position - supine, arm adducted
– Total of 20-30ml of LA
– Brachial plexus - cluster of hyperechoic round or ovoid structures surrounding the axillary artery, deep to pec minor with transducer inferior to the clavicle, approximately parasagittal
* Axillary
– Position - pillow behind shoulder, arm abducted and elbow flexed
– Total of 15-20ml of LA
– Probe transverse acorss the axilla at the junction of the biceps and pectoralis muscle, median (10), ulnar (2) and radial (6) nerve surround the axillary artery, radial nerve on top of the conjoined tendon, musculocutaneous nerve between biceps and coracobrachialis anteriorly.

Question 12

Tracheobronchial Tree

Answer 12

The Trachea
* Arises at the lower border of cricoid cartilage in the neck, as a continuation of the larynx
* Travels inferiorly into the superior mediastinum, bifurcating at the level of the sternal angle to form the right and left main bronchi
* Located anteriorly to the oesophagus, inclined slightly to the right
* Held open by C shaped rings, free end supported by the trachealis muscle
* Lined by ciliated pseudostratified columnar epithelium, interspersed by goblet cells which produce mucus
* Carina runs anterioposteriorly between the opens of the two bronchi
* Sensory innervation from the recurrent laryngeal nerve
* Arterial supply from the tracheal branches of the inferior thyroid artery
* Venous drainage via brachiocephalic, azygos and accessory hemoazygos veins

The Bronchi
* At the level of the sternal angle, bifurcates into the right and left main bronchi
* Further branch to secondary bronchi - each of which supplies a lobe of the lung and gives rise to several segmental bronchi
* Right main bronchus - wider, shorter, descends more vertically than L side
* Right superior lobus bronchus arises before the right main bronchus enters the hilum
* Left main bronchus - passes inferiorly to the arch of the aorta and anteriorly to the thoracic aortia and oesophagus
* Main bronchi –> lobar (secondary) bronchi - 3x R, 2x L –> segmental (tertiary) bronchi, each supplies a bronchopulmonary segment
* Main bronchi - cartilage rings completely encircle the lumen
* In lobar and segmental bronchi, cartilage is crescent shaped
* Innervation from the pulmonary branches of the vagus nerve
* Arterial supply from the bronchial arteries
* Venous drainage into the bronchial veins
* Total of 19 segments
* RUL - apical, posterior and anterior
* RML - lateral, medial
* RLL - anterobasal, laterobasal, posterobasal, mediobasal, superior
* LUL - apical, posterior and anterior
* Lingual lobe - superior and inferior
* LLL - Superior, posterobasal, laterobasal, anterobasal

The Bronchioles
* Smallest airways, contain no cartilage or mucus secreting goblet cells
* Club cells produce a surfactant lipoprotein to prevent the walls of the small airways sticking together during expiration
* Many generations of conducting bronchioles
* Terminal bronchioles branch into respiratory bronchioles with alveoli
* Alveoli are tiny air-filled pockets with thin walls (simple squamous epithelium) –> site of gas exchange
* ~300 million alveoli in adult lungs

Question 13

Carotid sinus and bodies

Answer 13

• Common carotid artery forms two specialised structures near its bifurcation
• Carotid sinus
  – dilation of the base of the internal carotid artery
  – baroreceptor
  – innervated by carotid branch of glossopharyngeal
  – relays information about arterial BP to the hypothalamus
• Carotid body
  – oval structure
  – posterior to carotid bifurcation
  – chemoreceptor
  – innervated by carotid branch of glossopharyngeal
  – surrounded by fibrous capsule, consists of multiple lobules, divided by septa
  – within each lobule - 2 types of cells
  – glomus (type 1) cells - involved in storing peptides and amines
  – sustenacular (type 2) cells) - separate the glomus cells from an extensive network of fenestrated sinusoids
  – relay information about the the arterial chemical composition to respiratory centres in the brainstem
  – stimulated by hypercapnia, hypoxia and low pH (increased H+ concentration)

Question 14

The Sacrum/Caudal

Answer 14

Sacrum
* Fusion of 5 sacral vertebrae
* Inverted triangular, concave shape
* Base - articulates superiorly with the 5th lumbar vertebra and its intervertebral disc
* Apex - abuts the coccyx inferiorly
* Auricular surfaces - located laterally on the sacrum, articulates with the auricular surface of the ilium
* Dorsal/posterior surface - coarse and rugged, 3 crests (median, lateral and intermediate), central ridge of bone, attachment for multifidus lumborum, erector spinae
* Pelvic/anterior surface - smooth surface with 4 transverse lines, attachment for piriformis, coccygeus and iliacus
* Internally - the central canal of the vertebral column continues to the 4th sacral foramina - sacral hiatus
– dural sac terminates at about S2 in adults, S4 in newborns, by age 2 similar to adult (increased risk of intrathecal injection in <2yrs)
– filum terminale continues inferiorly as the coccygeal ligament to attach at the coccyx
– sacral and coccygeal nerves make up cauda equina
– epidural fat - loose in children allowing for greater spread of LA, fibrosed in adults
– sacral epidural veins end at S4
* Two sympathetic autonomic trunks, each with four ganglia - underdeveloped autonomic nervous system in children reduces sympathetic blockade and hypotension
* Median and lateral sacral arteries (arise from posterior dividsion of internal iliac artery and give rise to superior and inferior branches)

Nerve supply
* Scrotum - anterior 1/3rd - ilioinguinal nerve (L1), posterior 2/3rds - perineal nerve (S2), lateral - posterior cutaneous nerve of the thigh (S3)
* Penis - dorsal nerve of penis (S2,3,4), ilioinguinal nerve

Sacral hiatus
* apex of an equilateral triangle drawn joining the PSIS, approx 5cm above the tip of the coccyx
* when the curve of the sacrum is followed in the midline with the tip of the finger from the tip of the coccyx, the sacral hiatus if felt as a depression
* superior boundary - fused laminae of S4
* lateral boundary - margins of the deficient laminae of S5
* inferior boundary - posterior surface of the body of S5
* posterior boundary - sacrococcygeal ligament

Caudal Block (can cover T10-S5)
* Prerequisites - consent, monitoring, IV access, trained assistant, equipment, emergency drugs
* Skin cleaning - full asepsis
* Prep-stop-block
* Armitage regimen to calculate - 0.25% levobupivacaine
– infraumbilical operation - 0.5ml/kg
– lower thoracic operation - 1ml/kg
– higher thoracic operation - 1.25ml/kg
* Additives - preservative free - opioids, clonidine, ketamine
* Position - lateral (prone in adults)
* Landmarks
* Procedure - 22G short bevelled cannula inserted at 45 degrees until a ‘click’ is felt (sacrococcygeal ligament pierced), direct needle cephalad, careful aspiration for blood or CSF, allow passive flow before slow injection

Question 15

Central venous access

Answer 15

Indications
* vascular access
* TPN
* infusion of irritant/hypertonic drugs
* CVP measurement
* cardiac catheterisation
* PA catheterisation
* TV cardiac pacing

Options
* CVC - IJ, femoral, SC, EJV (difficult due to valves)
* PICC - usually basilic or cephalic veins above the ACF

Internal Jugular Vein
* originates at the jugular bulb (formed by the confluence of the inferior petrosal sinus and the sigmoid sinus)
* exits the skull via the jugular foramen
* descends laterally to the internal carotid (and later the common carotid) in the carotid sheath
* terminates behind the sternal end of the clavicle, where it joins the subclavian vein to form the brachiocephalic vein
* Borders
– anterior - sternocleidomastoid
– posterior - lateral mass of C1, scalene muscles and lung pleura
– medial - internal carotid
* Relationships
– vagus nerve lies behind/between the carotid and IJV
– cervical sympathetic plexus lies posterior to the carotid sheath
– deep cervical lymph nodes lie close to the vein
– EJV crosses the sternomastoid belly of SCM, running posteriorly and more superficial to the IJV, later perforating deep fascia to drain into the subclavian
– pleura rises above the clavicle, and is close to the vein at its termination
– thoracic duct passes lateral to the confluence of LIJV and SCV, and may be injured during LIJV cannulation

Subclavian Vein
* continuation of the axillary vein as it crosses the upper surface of the first rib
* travels posterior to the clavicle, separated from the subclavian artery by the anterior scalene muscle
* joins with the IJV to form the brachiocephalic vein
* Borders
– anterior - clavicle, subclavius muscle, pec major
– posterior - anterior scalene and subclavian artery
– inferior - 1st rib and lung apex
– superior - skin, subcutaneous tissue, platysma
– medial - brachiocephalic vein
– lateral - axillary vein
* needle placed in deltopectoral groove, inferior and lateral to the middle third of the clavicle
* needle inserted shallowly, passing under the middle third of the clavicle, aiming at the sternal notch
* USS guided - cross sectional –> longitudinal axis for insertion

Femoral Vein
* As the popliteal vein enters the thigh, it becomes known as the femoral vein
* Situated anteriorly in the thigh, accompanying the femoral artery
* Profunda femoris vein drains blood from the thigh muscles into the distal section of the femoral vein
* Femoral vein leaves the thigh by running underneath the inguinal ligament, at which point it becomes the external iliac vein
* Borders
– anterior - fascia lata, superficial fascia, skin
– posterior - adductor longus, pectineus, psoas major and iliacus
– medial - femoral canal (lymphatics, adipose and connective tissue)
– lateral - femoral artery and nerve
– superior - inguinal ligament

Question 16

Cervical Plexus (+ Blocks)

Answer 16

The cervical plexus is formed by the anterior rami of cervical spinal nerves C1-C5. It innervates the diaphragm, provides motor supply to some neck muscles and cutaneous sensation to the skin of the head, neck and chest.

• Network of nerve fibres that supply innervation to some of the structures in the neck and trunk
• Located in the posterior triangle of the neck - halfway up sternocleidomastoid, within the prevertebral layer of cervical fascia
• On the anterior surface of the four upper cervical vertebra, resting on levator anguli scapule and scalenus medius muscles, covered by SCM muscle
• Paired spinal nerves leave the spinal cord via intervertebral foramina, then divides into anterior and posterior nerve fibres
• Formed by the anterior rami of cervical spinal nerves C1-C4

Sensory Branches
* lesser occiptal nerve (C2) - skin of neck and scalp posterosuperior to the clavicle
* great auricular nerve (C2+C3) - skin over the parotid, posterior aspect of the auricle, area of skin extending from the angle of the mandible to the mastoid process
* transverse cervical nerve (C2+C3) - skin covering the anterior triangle of the neck
* supraclavicular nerves (C3+C4) - skin over the neck and shoulder

Motor branches
* muscular branches to sternocleidomastoid, prevertebral and levator scapulae
* ansa cervicalis (C1-C3) - infrahyoid muscles
– sternohyoid nerve (C1-C3)
– sternothyroid nerve (C1-C3)
– geniohyoid nerve (via hypoglossal nerve) (C1)
– omohyoid nerve (C1-C3)
– thyrohyoid nerve (via hypoglossal nerve) (C1)
* phrenic nerve (C4 with little fibres from C3/5) - diaphragm, mediastinal pleura, pericardium of the heart

Superficial cervical plexus block
* Most commonly used for carotid endarterectomy (favoured/felt equivalent to deep block)
* 10-15ml of LA (3-5ml per each redirection/injection) - usually 0.25%
* Landmarks - mastoid process, transverse process of sixth cervical rib, posterior border of SCM muscle (draw lines between)
* Prerequisites - consent, monitoring, IV access, trained assistant, equipment, emergency drugs
* Skin cleaning
* Prep-stop-block
* Position - supine, head turned to contralateral side
* 22G 50mm needle
* Deposit 3ml LA at the midpoint of SCM, followed by 7ml subcutaneously in a caudad and cephalad direction along the posterior border of the muscle (“fan”)

Question 17

Cervical sympathetic chain

Answer 17

• Begin in the spinal cord
• Originate from the thoracic region T1-6
• Enter the sympathetic chain - spans from the base of the skull to the coccyx, formed by nerve fibres and ganglia (collections of nerve cell bodies)
• Superior cervical ganglia
  – posterior to the carotid artery
  – anterior to C1-4 vertebrae
  – internal and external caroid nerves
  – nerve to pharyngeal plexus, combines with branches from the vagus and glossopharyngeal
  – superior cardiac branch
  – nerves to cranial nerves II, III, IV, VI, IX
  – grey rami communicantes - distributes sympathetic fibres to the anterior rami of C1-C4
  – effector organs - eyeball, face, nasal glands, pharynx, glands of the palate and nasal cavity, salivatory glands, lacrimal glands, sweat glands, pineal glands, dilator pupillae, superior tarsal muscle, carotid body, heart, arterial smooth muscle (carotid arteries)
• Middle cervical ganglia
  – absent in some
  – anterior to inferior thyroid artery and C6 vertebra
  – grey rami communicantes - distributes sympathetic fibres to the anterior rami of C5 and C6
  – thyroid branches
  – middle cardiac branch
  – effector organs - larynx, trachea, pharynx, upper oesophagus, heart, arterial smooth muscle (inferior thyroid artery)
• Inferior cervical ganglia
  – siutated anteriorly to C7
  – occasionally fused with the first thoracic ganglion - cervicothoracic ganglion
  – gray rami communicantes - distributes sympathetic fibres to the anterior rami of C7, C8 and T1
  – branches to the subclavian and vertebral arteries - innervate the smooth muscle
  – inferior cardiac nerve
  – effector organs - heart, arterial smooth muscle

Question 18

Cervical Vertebrae/Lumbar Vertebrae

Answer 18

Vertebra
* Bony components
– vertebral body
– vertebral arch - formed by pedicles and laminae
– vertebral foramen align to form the vertebral canal
– spinous process projects posteriorly from the vertebral arch
– bilateral trasverse processes project posterolaterally from the intersection of pedicles and laminae
– bilateral superior articular processes
– bilateral inferior articular processes
* Ligamentous components
– anterior longitudinal ligament extends from pelvic surface of sacrum to anterior tubercle of C1
– posterior longitudinal ligament - runs within the vertebral canal along the posterior aspects of vertebral bodies from C2 to sacrum
– ligamentum flavum - binds the laminae of adjacent vertebrae together and forms part of the posterior of the vertebral canal
– interspinous ligaments - weak ligaments joining adjacent vertebrae
– supraspinous ligaments - strong ligaments, merge with nucal ligament in the neck
– intertransverse ligaments - connect adjacent transverse processes

Atlas (C1)
* no body/spinous process
* anterior and posterior arches
* 2x lateral masses (upper and lower facets)
* transverse atlantal ligament

Axis (C2)
* bifid spinous process
* thick, strong laminae and pedicles
* odontoid peg
* small transverse processes
* flat superior facets

C3-C6
* small, wide, oval body
* oval shaped, flat facets
* transverse processes pierced by foramina transversaria - transmit the vertebral arteries
* short, bifid spinous process
* triangular vertebral foramen

C7
* spinous process not bifid
* longer spinous process

Thoracic
* medium sized, increase in size from superior to inferior
* articulate with the ribs, demi facets articular with the heads of 2 different ribs
* spinous processes oriented obliquely inferiorly and posteriorly
* circular vertebral formamen

Lumbar
* very large kidney shaped vertebral bodies
* no transverse foramina, costal facets or bifid spinous processes
* shorter spinous processes, do not extend inferiorly below the level of the vertebral body
* triangular vertebral foramen

Question 19

Coeliac plexus (+block)

Answer 19

• Autonomic plexus consisting of para-aortic ganglia on the anterior surface of the abdominal aorta
• At the level of the first lumbar vertebra
• Found around the roots of the coeliac trunk, superior mesenteric artery and renal artery
• Parasympathetic, sympathetic and nociceptive fibres
• Supplies inferior part of oesophagus, stomach, pancreas, spleen, kidneys, liver, gallbladder and small intestine

Relations
* Anterior - stomach, lesser sac and omental bursa, IVC (right ganglion), splenic artery origin (left ganglion)
* Posterior - crura of the diaphragm and abdominal aorta
* Lateral - adrenal glands

• Parasympathetic - Vagus nerve (CN X) - anterior and posterior trunks
• Sympathetic - greater and lesser splanchnic nerves
  – Smaller coeliac plexus
  – Superior mesenteric plexus
  – Adrenocortical plexus

Coeliac Plexus Block
* Primarily used for pain palliation in patients with chronic abdominal pain, usually secondary to advanced cancers of upper abdominal viscera
* CT guided/fluoroscopy guided anterior or posterior approach
* IV sedation
* Supine/prone depending on approach
* 20-50ml of 50-100% ethanol, phenol, bupivicaine/lidocaine

Complications
* hypotension, bleeding (aorta/IVC), IV injection, organ puncture, paraplegia, diarrhoea

Question 20

Coronary Blood Supply

Answer 20

Arterial Blood Supply
* Origin - right and left aortic sinuses within the aorta (behind the leaflets of the aortic valve)
* Left coronary artery - initially branches to give the LAD, also gives off left marginal arterial and left circumflex
* In 20-25% of individuals, the left circumflex contributes to the posterior inter ventricular artery
* Posterior interventricular artery supplies right ventricle, left ventricle and posterior 1/3rd of interventricular septum.
* Right coronary artery - branches to form the right marginal artery anteriorly
* In 80-85% of individuals, it also branches into the posterior intraventricular artery posteriorly. Supplies RA, SA and AV nodes and posterior part of interventricular septum.
* Right marginal artery supplies apex of right ventricle.

MI Regions
* Inferior MI - RCA - II, III, aVF
* Anteropapical - Distal LAD - V3/V4
* Anteroseptal- LAD - V1/V2
* Anterolateral - circumflex - I, aVL, V5, V6
* Extensive anterior - Proximal LCA - I, aVL, V2-V6
* True posterior - RCA - Tall R in V1, V7-V9

Venous Blood Supply
* Coronary sinus (large venous structure on the posterior aspect of the heart) —> empties into the right atrium
* Great cardiac vein - originates at apex of heart and ascends in the anterior interventricular groove, curves. The left and continues onto the posterior surface of the heart.
* Small cardiac vein - located on the anterior surface, in a groove between the R atrium and R ventricle. Travels within this groove onto the posterior surface.
* Middle cardiac vein (posterior interventricular vein) - begins at apex of the heart and ascends in the posterior interventricular groove
* Posterior cardiac vein - located on the posterior surface of the left ventricle. Lies to the left of the middle cardiac vein.
* Thesbian veins - small, valveless veins that drain venous blood from the myocardium directly into the ventricles

Question 21

Cross Section of the Chest at T1 (Thoracic Inlet)

Answer 21

Anterior to trachea
* skin
* superficial and deep fascia
* manubrium
* sternohyoid and sternothyroid muscles
* thymus

On right
* right brachiocephalic artery and vein
* right phrenic and vagus nerves
* apex of right lung + pleura

On left
* left subclavian and common carotid arteries
* left brachiocephalic vein
* left phrenic and vagus nerves
* apex of left lung + pleura

Posterior
* thoracic duct
* oesophagus
* right and left recurrent laryngeal nerves
* T1 vertebra

Question 22

Cross section of the neck at C4

Answer 22

Anterior to trachea
* skin
* superficial and deep fascia
* thyroid isthmus
* edges of sternomastoid
* sternohyoid muscles
* inferior thyroid veins

Posterior
* oesophagus
* RLN

Lateral
* thyroid lobes, carotid sheath, inferior thyroid artery

Question 23

Erector spinae plane block

Answer 23

Erector spinae - group of muscles that run bilaterally from the skull to the pelvis and from the spinous to the transverse processes, extending the the ribs.
ESP block aims to block posterior rami of spinal nerves.

Indications
* unilateral analgesia for acute post-surgical, post-traumatic or chronic neuropathic pain originating from the chest wall
* bilateral analgesia if performed bilaterally

Performing the Block
* Prerequisites - consent, monitoring, IV access, trained assistant, equipment, emergency drugs
* Skin cleaning
* Prep-stop-block
* Position - sitting or lateral decubitus
* Probe sagittal about 3cm lateral to the midline at the middle of the desired dermatomal spread, find the ‘tombstone’ appearance rather than the rounded ribs
* 3 layers of muscles - trapezius, rhomboid, erector spinae
* Direct 16H Tuohy towards the transverse process at the desired level, LA should lift the erector spinae off the transverse process
* 30-40ml 0.25% for analgesia
* Insert catheter if desirable

Question 24

Eye/Orbit

Answer 24

Eyeball
* Spherical organ lying in the bony orbit
* Fibrous layer
– sclera - provides attachent for the extraocular muscles (white part of the eye)
– cornea - transparent, refracts light entering the eye
* Vascular layer
– choroid - connective tissue and blood vessels - nourishes the outer layers of the retina
– ciliary body - ciliary muscle (smooth muscle fibres) and ciliary processes - controls the shape of the lens and contributes to the formation of aqueous humour
– iris - circular with central pupil, between the lens and the cornea
* Inner layer - retina
– pigmented (outer) layer - single layer of cells around the whole inner surface of the eye, attached to the choroid and absorbs light
– neural (inner) layer - photoreceptors, posteriorly and laterally, only covers part of the retina
–> centre of retina = macula with fovea centralis (high acuit vision)
–> blind spot = where the optic nerve enters the retina

Internal structures
* Vitreous body - transparent gel which fills the posterior segment (posterior to the lens) - contributes to magnifying power of the eye, supports the lens, holds the layers of the retina in place
* Lens - anterior, between the vitreous humour and the pupil, shape altered by the ciliary body, altering its refractive power
* Anterior chamber - fluid filled area between the cornea and iris
* Posterior chamber - between the iris and ciliary processes
* Aqueous humour - produced constantly by the ciliary processes, secreted from the ciliary body, drains from the posterior chamber into the anterior chamber and then exits the eye through trabecular meshwork into Schlemm’s canal and then into episcleral veins

Bony Orbit
* Superior portion - frontal bone
* Lateral portion - zygoma and sphenoid bones
* Inferior portion - zygoma and maxilla
* Medial portion - ethmoidal and lactimal bones
* Contents - globe, orbital fat, muscles, nerves, vessels, lacrimal apparatus
* Supraorbital foramen (in the frontal bone) - supraorbital artery, vein and nerve
* Optic canal (in the sphenoid) - optic nerve, ophthalmic artery
* Superior orbital fissure - CN III, IV, VI, V1, superior ophthalmic vein
* Inferior orbital fissure - branches of CN V2, orbital branches of pterygopalatine ganglion, inferior ophthalmic vein, infraorbital artery and vein, tributary of pterygoid plexus
* Intraorbital foramen (in the zygoma) - infraorbital artery, vein and nerve, tributary of pterygoid plexus
* Anterior and posterior ethmoidal foramina - ethmoidal nerves and vessels

Innervation
* Motor
– CN III - levator palpebrae, SR, MR and IO
– CN IV - SO
– VI - LR
– VII - orbicularis oculi
* Sensory - trigeminal nerve
– V1 (ophthalmic division) - skin, conjunctiva, upper eyelid, cornea, iris, ciliary muscle, inner eyelid, inner canthus, outer eyelid
– V2 (maxillary division) - lower eyelid, nasolacrimal duct, lateral wall of orbit
* Autonomic
– sympathetic - long and short ciliary nerves from the superior cervical ganglion (mydriasis)
– parasympathetic - oculomotor (meiosis)

Blood supply
* Globe and orbital contents - ophthalmic artery (ICA)
* Central artery of the retina (a branch of ophthalmic) supplies the internal surface of the retina
* Venous drainage via superior and inferior ophthalmic veins –> cavernous sinus

Question 25

Facial Nerve

VII

Answer 25

• Temporal nerve - supples frontalis and procerus muscles
• Zygomatic - supplies eye and orbit, mid face and smile
• Buccal - supplies buccinator and upper lips
• Mandibular - supplies lower lip and orbicularis oculi
• Cervical - supplies platysma

Question 26

Fascial Iliaca Compartment

Answer 26

• Potential space within the pelvic brim
• Anterior - fascia lata, fascia iliaca (attaches to the iliac crest laterally and the fascia overlying the psoas muscle medally)
• Posterior - iliacus, psoas
• Contents - femoral nerve, obturator nerve, LCNT

Fascia Iliaca Compartment Block
* Prerequisites - consent, monitoring, IV access, trained assistant, equipment, emergency drugs
* Skin cleaning
* Prep-stop-block
* Position - supine, leg slightly externally located
* Large volume block (30-40ml)
* Landmark technique - line between ASIS and pubic tubercle divided into thirds - perform injection 1cm cephalad to the junction of the lateral third and medial two thirds - insert a blunt, short-bevel needle perpendicular to the skin then directed cranially at 60 degrees - 2x pops. Aspirate, inject
* US infrainguinal - identify femoral artery at inguinal crease, visualize femoral nerve below inguinal ligament, aim to insert needled 1-2cm lateral to femoral nerve (2x pops)
* US suprainguinal - transducer in para-sagittal plane over ASIS, insert needle from inferior to superior aiming to pass to just superior to the inguinal ligament (2-4cm)

Question 27

Femoral Triangle

Answer 27

• Wedge shaped area located within the superomedial aspect of the anterior thigh
• Acts as a conduit for structures entering and leaving the anterior thigh

Borders
* Roof - fascia lata
* Floor - pectineus, iliopsoas, adductor longus muscles
* Superior - inguinal ligament (runs from ASIS to pubic tubercle)
* Lateral - medial border of sartorius muscle
* Medial - medial border of adductor longus

Contents (lateral to medial)
* Femoral sheath - fascial compartment containing the following contents)
* Femoral nerve - innervates anterior compartment of thigh, sensory branches for leg and foot
* Femoral artery - majority of arterial supply to lower limb
* Femoral vein - great saphenous vein drains into the femoral vein
* Femoral canal - contains deep lymph nodes and vessels

Question 28

Fetal Circulation

Answer 28

• Placenta
• 1x umbilical vein (sats 80%)
• 40% of blood travels through liver to IVC
• 60% travels through ductus venosus to IVC
• IVC receives blood from the lower body
• SVC receives blood from the upper body
• IVC and SVC meet at the Eustachian Valve
• Blood travels through the foramen ovale to the left heart
• Blood also travels through the right heart
• From the right heart, 10% of the blood travels through the lungs and on into the left heart
• From the right heart, blood travels through the ductus arteriosus into the aorta to supply the lower body
• From the left heart, blood travels through the aortic arch to supply the upper and lower body
• Blood from the lower body returned to the placenta via 2x umbilical arteries (sats 40%)

Following clamping of the cord and aeration of the lungs
* SVR increases –> increased LV arterial afterload
* Movement of air into the lung –> pulmonary vasodilation –> decreased PVR and rapid increase in pulmonary blood flow –> shunting across ductus arterosus reverses –> increase in left atrial pressure causes closure of the foramen ovale
* DV becomes operationally ineffective due to decreased umbilical venous blood flow - closes permanently within the first 2 weeks (slower in preterm infants)
* FO closes and fuses with the interatrial septal wall making it operationally ineffective soon after birth - closes permanently within the first few years of life
* DA - increased oxygenation and a reduction in circulating prostaglandin levels facilitates contraction of smooth muscle and eventually closure of DA, supported by the flow reversal

Question 29

First rib

Answer 29

• Head articulates with vertebra
• Neck
• Tubercle posterolaterally
• Body of the rib wraps around the chest laterally and anteriorly
• Subclavian vein - groove most anterior on the upper surface
• Subclavian artery + lowest trunk of brachial plexus - posterior groove
• Anterior scalene artery attaches between the 2 grooves
• Middle scalene attaches to rough area on upper surface posterior to posterior groove
• Serratus anterior attaches to outer border of the rib

Question 30

Generic “Describe the anatomy of…”

Answer 30

• Size/weight
• Location
• Relations - anterior, posterior, medial, lateral, superior, inferior, superficial, deep
• Contents
• Blood Supply
• Venous drainage
• Nerve supply
• Lymphatic drainage
• Anything special

Question 31

Intercostal Block

Answer 31

Intercostal neuro vascular bundle (from superior to inferior)
* Vein
* Artery
* Nerve

Intercostal muscles
* External intercostal
* Internal intercostal
* Innermost intercostal

Question 32

Intraosseus Anatomy

Answer 32

Parts of a long bone
* epiphysis - filled with cancellous bone and covered by the cortex, a hard thin casing
* diaphysis - shaft of bone composed of a thick, hard cortex with a hollow interior space (the medullary cavity)
* epiphyseal plate - junction between the epiphysis and diaphysis where bone growth occurs

Structures passed through by IO
* skin
* subcutaneous tissue
* periosteum - layer of connective tissue
* cortical bone
* cancellous bone
* endosteum - layer of connective tissue
* medullary cavity - non collapsible entry point into the systemic venous system

Sites of insertion
* proximal tibial - anterior surface, 2-3cm below the tibial tuberosity and 1-2cm medial
* distal femoral - anterolateral surface, 3cm above lateral condyle
* proximal humeral - ~1cm above the surgical neck (hand rested palm down on the abdomen with elbow adducted)
* iliac crest, sternum

Question 33

Jugular Vein

Answer 33

• 3 jugular veins
• Venous drainage of the scalp and face - drained by veins synonymous with the arteries of the face and scalp –> empty into the internal and external jugular veins
• Venous drainage of the neck - anterior jugular veins

External jugular vein
* Supplies the majority of the external face
– posterior auricular vein (drains scalp superior and posterior to the outer ear)
– retromandibular vein - formed by the maxillary and superficial temporal veins (drain the face)
* EJV formed by these 2 veins combining immediately posterior to the angle of the mandible, inferior to the outer ear
* Descends down the neck within the superficial fascia
* Runs anterior to the sternocleidosmastoid muscle (crossing it in an oblique, posterior and inferior direction)
* Passes underneath the clavicle in the root of the neck
* Drains into the subclavian vein
* Receives tributary veins from posterior external jugular, transverse cervical and suprascapular

Anterior jugular veins
* Paired veins, drain the anterior aspect of the neck
* Often communicate via a jugular venous arch
* Descend down the midline of the neck, emptying into the subclavian vein

Internal jugular vein
* Begins in the cranial cavity as a continuation of the sigmoid sinus
* Initial part is dilated and known as the superior bulb
* Exits the skull via the jugular foramen
* Descends within the carotid sheath, deep to SCM and lateral to the common carotid artery
* At the base of the neck, posterior to the sternal end of the clavicle, combines with the subclavian vein to form the brachiocephalic vein
* Inferior end dilates to form inferior bulb (valve stops back-flow of blood)
* Receives blood from facial, lingual, occipital, superior and middle thyroid veins

Question 34

Larynx

Answer 34

• Located in the anterior compartment of the neck
• Suspended from the hyoid bone, spanning C3-C6
• Continuous inferiorly with the trachea, opens superiorly into the laryngeal part of the pharynx
• Covered anteriorly by infrahyoid muscles
• Covered laterally by lobes of the thyroid
• Primarily cartilaginous
• Held together by ligaments and membranes
• Important for phonation, cough reflex and protection of the LRTI as well as breathing
• Lined by pseudostratified ciliated columnar epithelium apart from true vocal cords which are lines by stratified squamous epithelium

Musculature
* Tensor muscles - circothyroid (ELM), vocalis
* Adductor muscles - posterior cricoarytenoid
* Abductor muscles - lateral cricoarytenoids, thyroarytenoid, interarytenoid

Internal cavity
* Supraglottis - inferior surface of epiglottis to vestibular folds (false vocal cords)
* Glottis - vocal cords and 1cm below
* Subglottis - inferior border of glottis to inferior border of cricoid cartilage

Vasculature
* Superior laryngeal artery (branch of superior thyroid artery, derived from external carotid)
* Inferior laryngeal artery (branch of inferior thyroid artery, derived from thyrocervical trunk)
* Superior laryngeal vein –> superior thyroid vein –> IJV
* Inferior laryngeal vein –> inferior thyroid vein –> left brachiocephalic vein

Innervation (vagus)
* Recurrent laryngeal nerve - thyroarytenoid, posterior cricoarytenoid, lateral cricoarytenoid, transverse and oblique arytenoids, vocalis, sensory innervation to the infraglottis
* Superior laryngeal nerve
– internal laryngeal nerve - sensory innervation to supraglottis
– external laryngeal nerve - cricothyroid muscle

Question 35

Liver

Answer 35

• Second largest organ in the body
• Weighs approximately 1.5kg (2.5% of body weight)
• Located in the right hypochondrium and epigastric areas, extending into the left hypochondrium
• Hepatocytes - polyhedral epithelial cells arranged in sheets separated from each other by spaces filled with hepatic sinusoids
• Hepatic sinusoids are vessels that arise at the portal triad (portal vein, hepatic artery and bile cannaliculi) and run between sheets of hepatoxytes receiving blood from the portal triad to deliver to the central vein
• Structural unit - liver lobule

Surfaces
* Diaphragmatic surface - anterosuperior surface of the liver
– smooth and convex, fits snugly beneath the curve of the diaphragm
– posterior aspect of the diaphragmatic surface is not covered by visceral peritoneum, in direct contact with the diaphragm
* Visceral surface - posteroinferior surfact of the liver
– covered with peritoneum (apart from the fossa of the gallbladder and porta hepatis)
– moulded by the shape of the surrounding organs, making it irregular and flat
– lies in contact with the R kidney, R adrenal gland, R colic flexure, transverse colon, 1st part of duodenum, gallbladder, oesophagus and stomach

Ligaments
* Formed by a double layer of peritoneum
* Falciform ligament - sickle shaped, attaches the anterior surface of the liver to the anterior abdominal wall, free edge contains ligamentum teres (remnant of the umbilical vein)
* Coronary ligament (anterior and posterior folds) - attach the superior surface of the liver to the inferior surface of the diaphragm, anterior and posterior folds unit to form the triangular ligaments
* Left triangular ligament - formed by the union of the anterior and posterior layers of the coronary ligament at the apex of the liver and attached the left lobe of the liver to the diaphragm
* Right triangular ligament - formed in a similar fashion adjacent to the bare area and attaches the right lobe of the liver to the diaphragm
* Lesser omentum - attaches the liver to the lesser curvature of the stomach and first part of the duodenum
– hepatoduodenal ligament - from the duodenum to the liver, surrounds the portal triad
– hepatogastric ligament - from the stomach to the liver
* Posterior surface of liver secured to the IVC by hepatic veins and fibrous tissue

Hepatic recesses
* anatomical spaces between the liver and surrounding structures
* Subphrenic spaces (left and right) - between the diaphragm and anterior and superior aspects of the liver, divided by the falciform ligament
* Subhepatic space - a subdivision of the supracolic compartment (above the transverse mesocolon), between the inferior surface of the liver and the transverse colon)
* Morison’s pouch - potential space between the visceral surface of the liver and the right kidney (pathological abdominal fluid collects here when supine)

Anatomical division
– right and left lobes divided by the falciform ligament
– two accessory lobes arise from the right lobe, separated by a deep, transverse fissure that transmits all the vessels, nerves and ducts entering or leaving the liver (excepting the hepatic veins) –> porta hepatis
– caudate lobe - upper aspect of visceral surface
– quadrate lobe - lower aspect of the visceral surface

Surgical division
– total of eight independent segments
– each segment has its own blood supply and biliary drainage
– each can be resected without damage to adjacent segments

Functional classification
* Classic lobule - based on direction of blood flow. Hexagonal structure with central vein in the middle and portal triad at six corners. Hepatic arterial and portal venous blood flows from the portal triad to the central vein
* Portal lobule - based on direction of bile flow. Portal triad in the middle and central veins form the corners of the triangle
* Hepatic acinus - based on changes in oxygen and nutrient content as blood flows from the portal triangle to the central vein
– two triangles of adjacent classic lobule, whose apices are the central veins
– forms a rhomboid shape
– hepatocytes divided into 3 zones
– zone 1/periportal zone - highest blood supply, susceptible to damage by blood-borne toxins and infection
– zone 2/intermediate zone
– zone 3/centrilobular zone - closer to the central vein, higher CYP450 levels but gets least blood supply and is susceptible to ischaemia

Vasculature
* Total liver blood flow 1200-1400mls/min (~25% of CO)
* Hepatic artery (25%) - supplies the non-parnchymal structures of the liver with arterial blood, derived from the coeliac trunk. High pressure, high resistance system.
* Hepatic portal vein (75%) - supplies the liver with partially deoxygenated blood, carrying nutrients absorbed from the small intestine. Low pressure/low resistance system. Formed by the union of superior mesenteric vein and splenic vein.
* Venous drainage of deoxygenated, detoxified blood through hepatic veins –> IVC

Innervation
* Parenchyma innervated by the hepatic plexus
– sympathetic (coeliac plexus) fibres
– parasympathetic (vagus nerve) fibres
* Glisson’s capsule - innervated by branches of the lower intercostal nerves

Lymphatic Drainage
* Anterior aspect drains into hepatic lymph nodes (lie along hepatic vessels and ducts, empty into coeliac lymph nodes –> cisterna chyli)
* Posterior aspect drains into phrenic and posterior mediastinal nodes –> right lymphatic and thoracic ducts

Question 36

Nervous Supply of the Lower Limb

Answer 36

Osteotomes
* Femur - femoral nerve, obturator nerve, sciatic nerve
* Tibia - femoral nerve, common peroneal nerve, tibial nerve
* Fibula - common peroneal nerve, tibial nerve
* Anterior ankle + phalanges - common peroneal nerve
* Posterior ankle - tibial nerve

Myotomes
* L2 - iliopsoas (bends hips)
* L3 - quadriceps femoris (straightens knee)
* L4 - anterior tibialis (pulls feet up)
* L5 - extensor digitii (wiggles toes)
* S1 - posterior tibialis (pulls feet down)

Sensory nerve supply
* Sciatic nerve - posterior thigh
* Lateral femoral cutaneous nerve - lateral thigh
* Femoral nerve - anterior and medial thigh and knee
* Obturator nerve - area of medial thigh
* Saphenous nerve - medial knee and anteromedial lower leg
* Common peroneal nerve - anterolateral lower leg, upper foot and toes
* Tibial nerve - posterior lower leg, heel, lateral foot, dorsum of foot

Dermotomes
* L1 - outer thigh
* L2 - inner thigh
* L3 - knee
* L4 - medial calf
* L5 - lateral calf
* S1 - lateral foot
* S2 - posterior heel

Question 37

Lumbar plexus

Answer 37

• Anterior rami of L1-L4
• Iliohypogastric nerve - L1 (T12) - internal oblique and transversus abdominis, posterolateral gluteal skin in the pubic region
• Ilioinguinal nerve - L1 - internal oblique and transversus abdominis, superior antero-medial thigh + root of penis/anterior scrotum/mons pubis/labia majora
• Genitofemoral - L1/2 - cremsteric muscle - genital branch, femoral branch (upper anterior thight)
• Lateral cutaneous nerve of the thigh - L2/3 - anterior and lateral thigh down to the knee
• Obturator nerve - L2/3/4 - medial thigh muscles and skin over medial thigh
• Femoral nerve - L2/3/4 - muscles of anterior thigh, skin on anterior thigh and medial leg

Question 38

Mediastinum

Answer 38

• Lies between the right and left pleurae
• Extends from the sternum to the vertebral column
• Contains all the thoracic viscera apart from the lungs

Superior mediastinum
* Above the manubriosternal angle
* Bounded posteriorly by T1-4
* Continuous with neck above
* Continuous with anterior and posterior mediastina below
* Organs - thymus, oesophageus, thoracic duct, trachea, bronchi
* Vessels - arch of aorta, brachiocephalic trunk, SVC, both brachiocephalic veins, left common carotid, left subclavian artery
* Nerves - both phrenic nerves and vagal nerves, left recurrent laryngeal nerve

Anterior mediastinum
* Between sternum anteriorly and pericardial sac posteriorly
* Contains the sternopericardial ligament, fat and lymph nodes

Middle mediastinum
* Between the anterior and posterior mediastinum
* Contains the pericardium, heart, phrenic nerves, pericardioacophrenic vessels and origin of the great vessels

Posterior mediastinum
* Between the pericardial sac and the anterior surface of the vertebral bodies
* Contains the descending aorta, oesophagus, azygous system of veins, vagus nerve, thoracic duct, lynph nodes and thoracic splanchnic nerves

Question 39

Neuraxial anaesthesia

Answer 39

Spinal epidural space
* space lying within the vertebral column that contains nerve roots, vessels and fat
* negative pressure space - continuous with the paravertebral space which is affected by changes in intrapleural pressure
* borders
– anterior - posterior longitudinal ligament, vertebral bodies and discs
– posterior - ligamentum flavum, facet joints and lamina
– superior - endosteal layer of dura (prevents passage of contents through foramen magnum)
– inferior - sacrococcygeal membrane at sacral hiatus
– lateral - pedicles and intervertebral foraminae

Contents
* loose alveolar connective tissue +/- scar tissue
* fat, in proportion to the rest of the body
* dura sac, containing CSF and Cauda equina
* spinal nerve roots as they exit the dura sac and pass through the intervertebral foramina; dorsal root ganglia in lateral recesses
* extensive plexus of veins - valveless and continuous with intracranial and pelvic veins
* arteries

Intrathecal space
* deep to epidural space
* contains spinal cord and CSF

Surface Anatomy
* spinous processes generally palpable in midline
* C2 first palpable
* C7 most prominent
* T7 tip of scapula with arms by side
* Line across iliac crest - L4/5

Layers
* skin
* subcutaneous tissue
* supraspinous ligament
* interspinous ligament
* ligamentum flavum
* epidural space
* dura
* subarachnoid space
* spinal cord (ends at L2 in adults, L3 in children)

Question 40

Oesophagus

Answer 40

• Fibromuscular tube
• Approximately 25cm in length
• Transports food from the pharynx to the stomach
• Originates at the inferior border of the cricoid cartilage (C6)
• Extends to the cardiac orifice of the stomach (T11)
• Enters the abdomen via the oesophageal hiatus (right crus of diaphragm) at T10
• Abdominal portion approximately 1.25cm long

Anatomical structure
* Adventitia - outer layer of connective tissue
* Muscle layer - external layer of longitudinal muscle (superior 1/3rd voluntary striated muscle, middle 1/3rd voluntary striated and smooth muscle, inferior 1/3rd smooth muscle) and inner layer of circular muscle
* Submucosa
* Mucosa - non-keratinised stratigied squamous epithelium (contiguous with columnar epithelium of the stomach)
* Upper oesophageal sphincter - striated muscle sphincter between the pharynx and oesophagus, produced by cricopharyngeus
* Lower oesophageal sphincter - gastro-oesophageal junction (T11) - functional sphincter (no sphincteric muscle) maintained by:
– angle of entry into the stomach,
– compression of walls of intra-abdominal section with positive intra-abdominal pressure
– prominent mucosal folds at GOJ
– right crus of diaphragm has a ‘pinch-cock’ effect
* 4 physiological constrictions - arch of aorta, bronchus (left main stem), cricoid cartilage, diaphragmatic hiatus

Anatomical relations
* Cervical and thoracic
– anterior - trachea, left RLN, pericardium
– posterior - thoracic vertebral bodies, thoracic duct, zygous veins, descending aorta
– right - pleura, terminal part of azygous vein
– left - subclavian artery, aortic arch, thoracic duct, pleura
* Abdominal
– anterior - left CN X, posterior surface of the heart
– posterior - right CN X, left crus of the diaphragm

Vasculature
* Thoracic - branches of the thoracic aorta and inferior thyroid artery (branch of thyrocervical trunk)
* Drainage via branches of the azygous veins and inferior thyroid vein
* Abdominal - left gastric artery (branch of the coeliac trunk) and left infeior phrenic artery
* Drainage to the portal circulation via left gastric vein
* Drainage to the systemic circulation via the azygous vein

Innervation
* Oesophageal plexus
– parasympathetic vagal trunks
– sympathetic fibres from the cervical and thoracic sympathetic trunks
* Upper oesophageal sphincter and upper striated muscle - fibres from the nucleus ambiguus
* Lower oesophageal sphincter and smooth muscle - dorsal motor nucleus

Lymphatics
* Superior third - deep cervical lymph nodes
* Middle third - superior and posterior mediastinal nodes
* Lower third - left gastric and coeliac nodes

Question 41

Pain pathways

Answer 41

General pain pathway
- first order neurone - cell bodies within the dorsal root ganglion, nocicieptors activated through noxious stimuli (mechanical, chemical, thermal, mechano-thermal or polymodal nociceptors). A-delta fibres terminate in Rexed laminae I, releasing glutamate. C fibres terminate in Rexed laminae II (substantia gelatinosa), releasing substance P.
- second order neurone - cell bodies found in the rexed laminae of the spinal cord or in the nuclei of the cranial nerves within the brain stem - decussate in the anterior white commissure of the spinal cord and ascend in the spinothalamic tract to the ventral posterolateral nucleus of the thalamus.
- third order neurone - lie within the ventral posterolateral nucleus of the thalamus, terminate in the ipsilateral postcentral gyrus (primary somatosensory cortex)
- spinoreticular, spinomesencephalic and spinohypothalamic tracts + cervicothalamic tracts

Descending Modulation of Pain
* Opioid receptors (periaqueductal grey in the midbrain and rostral ventromedial medulla) - mu, kappa and delta
* Reduce neurotransmitter release from the first order neurone
* Cause hyperpolarisation of second order neurone
* Reduces firing of action potentials, blocking the transmission of pain signals
* Gate controltheory of pain - activation of A-beta fibres with tactile, non-noxious stimuli leads to activation of inhibitory interneurones in the dorsal horn, inhibiting pain signals transmitted via C fibres.

Question 42

Parathyroids

Answer 42

• Anterior neck, flattened and oval shaped
• Produce PTH - under hormonal control
• Posterior aspect of thyroid gland, external to it but within the pretracheal fascia
• 2x superior parathyroid glands - middle of the posterior borner of each thyroid lobe
• 2x inferior parathyroid glands - usually near the inferior poles, can be found in superior mediastinum
• Arterial supply - inferior thyroid artery, superior thyroid artery and thyroid ima artery
• Drain into superior, middle and inferior thyroid veins
• Lymphatic drainage to the paratracheal and deep cervical nodes
• Vasomotor nervous supply from thyroid branches of the cervical ganglia

Question 43

Paravertebral Space (+ Block)

Answer 43

A wedge shaped space adjacent to the spine on either side of the vertebral column

Boundaries
* Apex (lateral) - posterior intercostal membrane and intercostal space
* Base (medial) - vertebral body, intervertebral disc, vertebral foramen with corresponding spinal nerve
* Anterior - parietal and visceral pleura, lung parenchyma
* Posterior - transverse processes of the vertebra, heads of ribs and superior costotransverse ligament

Communications
* epidural space medially through the intervertebral foramina
* epidural space laterally through the intercostal spaces

Contents
* fatty tissue
* intercostal spinal nerves
* dorsal rami
* intercostal vessels
* rami communicantes
* sympathetic chain (at the neck of the rib anterior to the intercostal neurovascular bundle)

Paravertebral Block
* VATS - T3-T8 depending on site of operation
* Muscle sparing thoracotomy - incision about 5-7cm long extending vertically from T2 to T9
* Posterolateral thoracotomy - incision spans over at least 6 dermatomal levels T3 posteriorly to T8 anteriorly, chest drains placed at 8/9th ICS
* Total mastectomy/minimally invasive surgery - T1-T6/T7
* Renal/ureteric/appendix surgery - T10-L1
* Cholecystectomy/hepatic surgery - T6-T7
* Small volume, multiple injection technique to cover several dermatomes
* 20-25ml of local anaesthetic at a single level will cover approximately 4-5 dermatomes
* Multiple injection technique of 4-5ml of 0.25% L-bupivicaine for analgesia

Technique
* Prerequisites - consent, monitoring, IV access, trained assistant, equipment, emergency drugs
* Position - seated or lateral decubitus (side to be blocked uppermost), supported by attendant
* Mark skin at tips of spinous processes and at points 2.5-3cm lateral to these at the relevant levels to be blocked (these points should correspond with the transverse processes)
* Strict aspesis
* Prep-stop-block
* 2% lidocaine to skin at injection site
* 16 or 18G Tuohy needle advanced perpendicular to the skin until contact with the transverse process is established
* Change of resistance to saline technique used as the needle is ‘walked off’ the structure in a caudad and lateral direction and advanced approximately 1-1.5cm
* As the costotransverse ligament is penetrated, a ‘pop’ is felt as the needle enters the paravertebral space
* Careful aspiration to confirme the needle tip is not intravascular or intrathecal
* Administer LA

Question 44

Percutaneous Tracheostomy

Answer 44

• The larynx is an organ of phonation, also acting as a valve between the upper and lower airways.
• It is innervated by branches of the vagus nerve
• Superior laryngeal nerve provides sensation of the upper part (above the vocal folds) and motor of cricothyroid (addicts cords)
• Recurrent laryngeal nerve provides sensation to the lower larynx, and motor to the intrinsic muscles
• Superiorly, strap muscles and epiglottis attach to the hyoid
• Thyrohyoid membrane passes causally to thyroid cartilage
• Vocal cords attach anteriorly to the thyroid cartilage and pass posteriorly to the arytenoid cartilage, articulating below with the cricoid cartilage
• The cricothyroid membrane passes anteriorly between the thyroid and cricoid cartilages
• Cricotracheal ligament attaches the cricoid to the 1st tracheal ring
• Below the larynx, trachea passes behind the thyroid isthmus, backwards and downwards, anterior to the oesophagus to enter the thoracic cavity at the eternal notch
• Trachea originates at C6, bifurcates into 2 main bronchi at the level of T6 in inspiration
• 15-20 C shaped cartilages joined by fibrosis-elastic tissue, closed posteriorly by trachealis muscle
• Lined with ciliated columnar epithelium

Question 45

Pituitary

Answer 45

• “Master gland”
• Secretes hormones that control most of the body functions
• Pea sized organ suspended from the underside of the brain by the pituitary stalk
• Sits beneath the hypothalamus in the sella turcica (depression in the base of the skull)
• Superior surface of the gland is covered by a reflection of the dura mater
• Nerve supply from the carotid plexus of the sympathetic system

Relations
* Anterior - sphenoid sinus
* Posterior - posterior intercavernous sinus, dorsum sellae, basilar artery, pons
* Superior - diaphragma sellae, optic chiasm
* Inferior - sphenoid sinus
* Lateral - cavernous sinus, ICA, CN III, IV, V1, V2 and VI

Tissues
* 2 types of tissues - forming anterior and posterior
* Anterior - evagination of the ectodermal Rathke’s pouch containing epithelial tissue
– somatotropes - produce GH
– lactotropes - secrete PRL
– thyrotropes - TSH
– gonadotropes - LF/FSH
– corticotropes - ACTH
* Divided into 3 parts
– pars anterior - largest part, responsible for hormone secretion
– pars intermedia - thin epithelial layer that separates pars anterior from the psoterior lobe
– pars tuberalis - upward extension of the pars anterior that surrounds the anterolateral aspect of the stalk
* Posterior - extension of the brain at the level of the diencephalon containing neural tissue
– pituicytes (similar to glial cells)
– stores and releases oxytocin (produced by the paraventricular nucleus) and ADH (produced by the supraoptic nucleus)
– hormones stored in Herring bodies, closely associated with fenestrated capillaries

Blood supply
* anterior pituitary - superior hypophyseal artery
* hypothalamo-hypophyseal portal circulatory system - primary capillary network at the pituitary stalk, drained by a set of long portal veins into a second capillary bed in the anterior pituitary
* veins originating in the neurohypophyseal capillary plexus give rise to short portal veins that also contribute to the adenohypophyseal capillary plexus and connext the two circulatory systems
* infundibulum and posterior pituitary gland - superior hypophyseal artery, infundibular artery, inferior hypophyseal artery (branches of ICA)
* venous drainage –> cavernous sinus –> petrosal sinus –> jugular vein

Question 46

Popliteal fossa

Answer 46

• Diamond shaped area
• Posterior aspect of the knee

Borders
* Superomedial - semimemranosus
* Superolateral - biceps femoris
* Inferomedial - medial head of gastrocnemius
* Inferolateral - lateral head of gastrocnemius and plantaris
* Floor - posterior surface of knee joint capsule, popliteus muscle and posterior femur
* Roof - popliteal fascia and skin

Contents (medial to lateral)
* Popliteal artery
* Popliteal vein
* Tibial nerve
* Common fibular/peroneal nerve

Question 47

Sciatic nerve

Answer 47

• Nerve roots L4-S3
• Motor functions
  – muscles of posterior thigh and hamstring portion of adductor magnus
  – indirectly innervates all the muscles of the leg and foot
• Sensory functions
  – indirectly innervates the skin of the lateral leg, heel and both the dorsal and plantar surfaces of the foot
• Derived from the lumbosacral plexus
• Leaves the pelvis and enters the gluteal region via the greater sciatic foramen
• Emerges inferiorly to piriformis
• Descends inferolaterally
• Crosses the posterior surface of the superior gemellus, obturator internus, inferior gemellus and quadratus femoris muscles
• Enters the posterior thigh by passing deep to the long head of the biceps femoris
• At the apex of the popliteal fossa, bifurcates into the tibial and common fibular nerves

Sciatic Nerve Block - US guided approaches
* parasacral - sacral plexus block at the level of the greater sciatic foramen with patient in lateral decubitus position
* subgluteal - patient in lateral position, subgluteal space visualised and sciatic nerve sitting on top of the hypoechoic quadratus femoris muscle
* anterior - proximal thigh, advanced technique due to depth of target
* popliteal - supine, lateral or prone position, sciatic nerve followed from popliteal fossa, “tiger eye”
* volume of 20-30ml of LA

Question 48

Sacral plexus

Answer 48

• Anterior rami of sacral spinal nerves S1-S4
• Receives contributions from L4 and L5
• Superior gluteal nerve - L4-S1 - gluteus minimus, medius and tensor fascia lata (pure motor)
• Inferior gluteal nerve - L5-S2 - gluteus maximus (pure motor)
• Sciatic nerve L4-S3 - tibial portion - posterior compartment of thigh, leg and sole of foot, posterolateral leg, lateral foot and sole of foot sensation; common fibular portion - muscles in anterior and lateral compartments of the leg, skin of lateral leg and dorsum of foot
• Posterior femoral cutaneous - S1-3 - skin on posterior surface of thigh and leg, skin of perineum
• Pudendal nerve - S2-4 - skeletal muscles in perineum, external sphincters and levator ani, penis, clitoris and most of the perineal skin
• Nerve to piriformis, nerve to obturator internus and nerve to quadratus femoris

Question 49

Skull Foramina

What emerges from where?

Answer 49

• Cribriform plate - CN I, anterior ethmoidal nerves
• Optic canal - CN II, ophthalmic artery, central retinal vein
• Superior orbital fissure - CN III, CN IV, CN V1 (ophthalmic nerve), CN VI, superior ophthalmic vein
• Foramen rotundum - CN V2 (maxillary nerve)
• Foramen ovale - CN V3 (mandibular nerve)
• Foramen spinosum - middle meningeal artery, middle meningeal vein, meningeal branch of CN V3
• Internal acoustic meatus - CN VII, CN VIII, vestibular ganglion, labyrinthing artery
• Foramen magnum - spinal division of CN XI, medulla, meninges, vertebral arteries, anterior and posterior spinal arteries, dural veins
• Hypoglossal canal - CN XII
• Jugular foramen - CN IX, CN X, cranial division CN XI, jugular bulb, inferior petrosal and sigmoid sinuses

Question 50

The Spinal Cord

Answer 50

• A cylinder roughly 45cm long and 1cm wide
• Extends from the external margin of the formaen magnum as a continuation of the medulla oblongata, down to the L2 vertebral level
• It is entirely housed in the spinal meningeal layers
• As the spinal cord reaches L1, it turns into the conus medullaris - this is short, and at L2 sends off the remaining spinal nerves of L2-Co1 (the cauda equina)
• Conduit for sensory nerves travelling towards the brain and motor nerves travelling away from the brain
• Contains grey and white matter
• Grey matter - high density of neuron cell bodies and low density of axonal tracts
  – ventral horn - motor nerve cells
  – dorsal horn - sensory nerve cells
  – dorsal and ventral horns –> dorsal and ventral roots –> spinal nerve –> dorsal and ventral rami
• White matter - high density of myelinated axonal tracts and low density of neuron cell bodies
  – separated into tracts and fasciculi that ascend and descend

Descending
* Motor -pyramidal tracts –> crosses at the medulla
* Motor - extrapyramidal tracts –> reticulospinal and vestibulospinal do not decussate, rubrospinal and tectospinal decussate

Ascending
* Sensory - spinothalamic tract (pain, temperature, crude touch) –> crosses at the dorsal horn
* Sensory - dorsal column (vibration, proprioception, light touch) –> crosses at the medulla
* Sensory - spinocerebellar (proprioceptive - muscle stretch information) –> ventral spinocerebellar tract decussates twice, other tracts do not decussate, terminate in the ipsilateral cerebellum

Meningeal Layers
* osseus vertebral canal
* epidural space (containing loose areolar connective tissue and internal vertebral venous plexus)
* dura mater - tough, thick opaque layer of connective tissue (superficial)
* subdural space (containing CSF)
* arachnoid mater
* subarachnoid space
* pia mater - adheres to the spinal cord, extends ~20cm to the coccyx as the filum terminale (deep)

Question 51

Spleen

Answer 51

• Organ located in the upper left abdomen
• Roughly the size of a clenched fist
• 100-150g
• Under the diaphgragm and rib cage
• Intraperitoneal organ (ecxept at splenic hilum)
• Connected to stomach and kidneys by parts of the greater omentum (gastrosplenic ligament, splenorenal ligament)
• Slightly oval shape, covered by a weak capsule
• Diaphragmatic surface + visceral surface

Relations
* Anterior - stomach
* Posterior - diaphragm, left lung, ribs 9-11
* Inferior - left splenic flexure
* Medial - left kidney, tail of pancreas

Vasculature
* Primarily from the splenic artery (arises from the coeliac trunk)
* Branches into 5 vessels that do not anastomose with each other
* Drainage via the splenic vein –> superior mesenteric vein –> hepatic potal vein

Innervation
* Coeliac plexus

Lymphatics
* Follow the splenic vessels
* Drain into pancreaticosplenic lymph nodes –> coeliac nodes

Question 52

Stellate ganglion (+block)

Answer 52

• The stellate ganglion is a sympathetic ganglion formed by the fusion of the inferior cervical ganglion and the first thoracic ganglion.
• It lies at the level of C7.

Indications for a stellate ganglion block
* Pain syndromes (CRPS, refractory angina, herpres zoster)
* Vascular insufficiency (Reynaud’s syndrome, scleroderma, trauma)

Following successful stellate ganglion block
* Horner’s Syndrome - meiosis, partial ptosis, anhydrosis

Question 53

The Diaphragm

Answer 53

• Double domed musculotendinous sheet
• Inferior-most aspect of the rib cage
• Separates the thoracic cavity from the abdominal cavity
• Undergoes contraction and relaxation, altering the volume of the thoracic cavity and the lungs, producing inspiration and expiration

Attachments
* Peripheral
– bodies of lumbar vertebra L1-L3 and medial and lower arcuate ligaments, anterior longitudinal ligament
– internal surfaces of lower costal cartilages and ribs 7-12
– posterior aspect of xiphoid process of sternum
* Central
– central tendon

Relations
* pleural cavities
* pericardial sac
* liver
* kidneys
* adrenal glands
* stomach
* spleen

Openings
* Caval hiatus (T8) - IVC, terminal branches of right phrenic nerve
* Oesophageal hiatus (T10) - oesophagus, right and left vagus nerves, oesophageal branches of left gastric artery/vein
* Aortic hiatus (T12) - aorta, thoracic duct, azygos vein

Innervation
* Phrenic nerves (C3-5)
* Sensory innervation of peripheries via 6-11th intercostal nerves

Blood supply
* Subcostal arteries
* Lowest 5 intercostal arteries
* Inferior phrenic arteries arise directly from abdominal aorta
* Superior phrenic arteries
* Pericardiophrenic arteries
* Musculophrenic arteries
* Draining veins follow the arteries

Question 54

The Lungs

Answer 54

• Roughly cone shaped
• Left lung slightly smaller than right

Structure
* Apex - projects upwards, above the level of the 1st rib and into the floor of the neck
* Base - inferior surface of the lung, sits on the diaphragm
* Lobes (R x3, L x2) - separated by fissures
* Surfaces (x3) - correspond to the area of the thorax that they face - costal, mediastinal, diaphragmatic
* Borders (x3) - edges of the lung - anterior, inferior, posterior

Lobes
* 3x right - divided by oblique fissure and horizontal fissure
– Right superior
– Right middle
– Right inferior
* 2x left - divided by oblique fissure
– Left superior
– Left inferior

Vasculature
* Supplied with deoxygenated blood by the paired pulmonary arteries
* Following oxygenation, blood leaves the lungs via four pulmonary veins
* Bronchi, lung roots, visceral pleura and supporting lung tissues are suppled by bronchial arteries (from the descending aorta)
* Venous drainage via bronchial veins into azygous vein on right and accessory hemiazygos vein on left

Innervation
* Puulmonary plexuses
* Parasympathetic fibres from vagus nerve –> stimulate secretion from bronchial glands, contraction of bronchial smooth muscle and vasodilatation of pulmonary vessels
* Sympathetic fibres from the sympathetic trunks –> stimulate relaxation of the bronchial smooth muscle and vasoconstriction of the pulmonary vessels
* Visceral afferents - conduct pain impulses to the sensory ganglion of the vagus nerve

Lymphatic drainage
* Superficial (subpleural) plexus –> lung parenchyma
* Deep plexus –> structures of the lung root
* Empty into tracheobronchial nodes –> right and left bronchomediastinal trunks

Question 55

The Lymphatic System

Answer 55

• Series of vessels and nodes that collect and filter excess tissue fluid (lymph) before returning it to the venous circulation
• Vital part of the body’s immune defence

Organs
* Spleen - blood filter, removal of old RBCs, immune response
* Thymus - development and maturation of T lymphocyte cells
* Red bone marrow - maturation of immature lymphocytes
* Tonsils
* Appendix
* Walls of the GI tract

Lymph nodes
* Kidney shaped structures
* Filter foreign particles from the blood
* Average adult has 400-450
* Each contains T lymphocytes, B lymphocytes and other immune cells
* Lymph fluid enters through the afferent lymphatic channels and leaves via efferent channels

Lymph vessels
* Superficial - arise in the subcutaneous tissue, tend to accompany venous flow –> drain into deep vessels
* Deep - drain the deeper structures of the body, tend to accompany deep arteries
* Lymph channels (blind ended capillaries) –> vessels that travel proximally, draining through several lymph nodes –> empty into lymphatic trunks –> converge to form the right lymphatic duct and the thoracic duct
* Right lymphatic duct - drains lymph from the upper right quadrant of the body, including the right side of the head and neck, right side of thorax and right upper limb –> drains into the right subclavian vein via the right venous angle
* Thoracic duct - drains lymph from the rest of the body –> drains into the left subclavian vein via the left venous angle

Lymph fluid
* Transudative fluid that is transparent and yellow
* Formed when fluid leaves the capillary bed in tissues due to hydrostatic pressure
* Roughly 10% of blood volume becomes lymph
* Composition of lymph fairly similar to blood plasma
* 95% water
* 5% proteins, lipids, carbohydrates (mainly glucose), various ions and some cells (lymphocytes)
* Chyle - lymph from the GI system - particularly rich in fats
* Average 3-4 litres produced daily

Question 56

The Nose

Answer 56

• Pyramidal structure
• Nasal root located superiorly, continuous with the forebead
• Apex of the nose ends inferiorly in a rounded tip
• Inferior to the apex are the nares - piriform openings into the vestibule of the nasal cavity
• Bony component superiorly - contributions from the nasal bones, maxillae and frontal bone
• Cartilaginous component inferiorly - two lateral cartilages, two alar cartilages and one septal cartilage, smaller alar cartilages also
• Skin over the bone and cartilage, extending into the vestibule via the nares, with hairs to filter air

External nose
* small muscles insert into the external nose, contributing to facial expression
* – all innervated by branches of the facial nerve
* arterial supply from branches of the maxillary and ophthalmic arteries –> facial artery –> external carotid artery
* venous draining into the facial vein –> IJV
* lymphatic drainage via superficial lymphatic vessels accompanying the facial vein –> deep cervical lymph nodes
* sensory inntervation from the trigeminal nerve - external nasal nerve (branch of the ophthalmic nerve CN V1) and infraorbital nerve (branch of the maxillary nerve CN V2)

Nasal cavity
Divisions
* vestibule - area surrounding the anterior external opening to the nasal cavity
* respiratory region - lined by ciliated pseudostratified epithelium, interspersed with mucus-secreting goblet cells
* olfactory region - apex of the nasal cavity, lined by olfactory cells with olfactory receptors

Borders
* roof - nasal, frontal, sphenoid and ethmoid bones (cribriform foramina)
* floor - maxilla and palatine bones
* medial wall (nasal septum) - formed by the perpendicular plate of the ethmoid bone, the vomer bone and the septal cartilage
* lateral wall - 3 turbinates that project into the nasal cavity - inferior, middle, superior (increase the surface area for humidification)
* in continuity with nasopharynx posteriorly

Openings
* paranasal sinuses drain into the lateral walls of the nasal cavity (frontal, maxillary, ethmoidal)
* sphenoid sinus drains onto the posterior roof
* nasolacrimal duct opens into the inferior meatus
* eustachian (auditory) tube opens into the nasopharynx at the level of the inferior meatus

Vasculature
* branches of the internal carotid - anterior and posterior ethmoidal arteries (from the ophthalmic artery)
* branches from the external carotid - sphenopalatine artery, greater palatine artery, superior labial arterial, lateral nasal arteries
* Little’s area - area of rich blood supply in the anterior third of the nasal cavity that is most at risk of epistaxis
* venous drainage from veins that follow the arteries –> pterygoid plexus, facial vein or cavernous sinus

Innervation
* olfactory nerves –> olfactory bulb (on the superior surface of the cribriform flate)
* nasopalatine nerve (from the maxillary nerve)
* nasociliary nerve (from the ophthalmic nerve)

Question 57

The Peritoneum

Answer 57

• Continuous membrane which lines the abdominal cavity and covers the abdominal viscera
• Supports the viscera and provides pathways for blood vessels and lymph to travel to and from the viscera
• Two layers - continuous with each other - made up of simple squamous epithelial cells
• Parietal peritoneum - lines the internal surface of the abdominopelvic wall
• Parietal peritoneum receives the same somatic nerve supply as the region of the abdominal wall that it lines, sensitive to pressure, pain, laceration and temperature (well localised)
• Visceral peritoneum - covers the majority of the abdominal viscera
• Visceral peritoneum has the same autonomic nerve supply as the viscera it covers, sensitive to stretch and chemical irritation (poorly localised)
• Pain from the visceral peritoneum is referred to areas of skin (dermatomes) which are supplied by the same sensory ganglia and spinal cord segments as the nerve fibres innervating the viscera
• Peritoneal cavity - a potential space between the parietal and visceral peritoneum, normally contains only a small amount of lubricating fluid
• Intraperitoneal organs - have visceral peritoneum both anteriorly and posteriorly - stomach, liver, spleen
• Retroperitoneal organs - developed and remain outside the parietal peritoneam - oesophagus, rectum, kidneys
• Retroperitoneal organs - anterior surface covered with peritoneum - ascending and descending colon, adrenal glands, aorta/IVC, duodenum, pancreas, ureters, kidneys

Question 58

The Pharynx

Answer 58

• Muscular tube that connects the oral and nasal cavity to the larynx and oesophagus
• Begins at the skull and ends at the inferior border of the cricoid cartilage (C6)
• Nasopharynx - between the base of skull and soft palate, lined with respiratory epithelium, adenoid tonsils posterosuperiorly
• Oropharynx - between the soft palate and the superior border of the epiglottis
  – posterior one-third of tongue
  – lingual tonsils - lymphoid tissue at the base of the tongue
  – palatine tonsils - lymphoid tissue in the tonsillar fossa (between the palatoglossal and palatopharyngeal arches of the oral cavity)
  – superior constrictor muscle
• Laryngopharynx/Hypopharynx - between the superior border of the epiglottis and inferior border of the cricoid cartilage, continuous inferiorly with the oesophagus
  – middle and inferior pharyngeal constrictors
  – communicates with the larynx via the laryngeal inlet

Muscles
* Innervated by vagus nerve (apart from stylopharyngeus which is innervated by the glossopharyngeal nerve)
* Circular - contract sequentially to constrict the pharyngeal lumen and propel a food bolus inferiorly (CN X)
– superior - in the oropharynx
– middle - laryngopharynx
– inferior - thyropharyngeal and cricopharyngeal fibres, in the laryngopharynx
* Longitudinal
– stylopharyngeus - from styloid process of temporal bone into the pharyngeal wall (CN IX)
– palatopharyngeus - from the hard palate into the pharyngeal wall (CN X)
– salpingopharyngeus - originates from the eustachian tube and inserts into the pharyngeal wall (CN X)

Innervation
* Pharyngeal plexus
– pharyngeal branches from the glossopharyngeal nerve (CN IX)
– pharyngeal branch of the vagus nerve (CN X)
– branches from the external laryngeal nerve
– sympathetic fibres from the superior cervical ganglion
* Sensory innervation primarily from the glossopharyngeal nerve
* Anterior and superior aspect of the nasopharynx innervated by the maxillary nerve (CN V2)
* Inferior aspect of the laryngopharynx innervated by the internal branch of the vagus nerve

Vasculature
* Branches of the external carotid artery
– ascending pharyngeal artery
– branches of the facial artery
– branches of the lingual and maxillary arteries
* Venous drainage via the pharyngeal venous plexus –> IJV

Question 59

The Pleura

Answer 59

• Serous membranes covering the lung, mediastinum, diaphragm and the inside of the chest wall
• Two layers that meet at the lung hilum
  – visceral - attached closely and adheres to the whole surface of the lung, enveloping the interlobar fissure
  – parietal - attached to the chest wall and the diaphragm (names as mediastinal, diaphragmatic, costal and cervical pleura)
• Potential space between the 2 layers - pleural space
  – 0.2ml/kg of fluid (5-10ml)
  – determined by the net result of opposing Starling’s hydrostatic and oncotic forces and lymphatic drainage
  – serves as a lubricant and decreases friction between the pleurae during respiration
• Visceral pleura is supplied by bronchial arteries and drains into pulmonary veins
• Parietal pleura is supplied by systemic capillaries (intercostal, pericardiophrenic, musculophrenic, internal mammary vessels) and drains via the intercostal and azygous veins into the SVC and IVC
• Visceral pleura is supplied by the pulmonary branch of the vagus nerve and the sympathetic trunk (no pain fibres)
• Parietal pleura is innervated by the somatic intercostal and phrenic nerves

Question 60

The Safe Triangle

Chest drain insertion, finger thoracostomies

Answer 60

• Anterior - lateral border of pec major
• Lateral - anterior border of lat dorsi/mid axillary line
• Inferior - 5th intercostal space (diaphragm rises to 5th rib on expiration)
• Apex - base of the axilla
• Layers - skin, subcutaneous tissue, intercostal muscles, parietal pleura
• Intercostal bundle sits on the inferior aspect of the ribs so aim for above the lower rib

Question 61

The Tongue

Answer 61

• Muscular structure located on the floor of the oral cavity
• Primary taste organ and key role in the initial phases of swallowing
• 4 paired intrinsic muscles that affect the shape and size of tongue and have a role in facilitating speech, eating and swallowing - hypoglossal nerve CN XII
• Extrinsic muscles originate from structures outside the tongue and insert onto it - innervated by hypoglossal nerve apart from palatoglossus (CN X)
• Genioglossus, hypoglossus, styloglossus, palatoglossus
• Anterior 2/3rds general sensation - trigeminal nerve (lingual branch of the mandibular nerve CN V3)
• Anterior 2/3rds taste - facial nerve (chorda tmpani which travels through the middle ear)
• Posterior 1/3rd taste and sensation - glossopharyngeal CN IX
• Lingual artery (branch of external carotid) + tonsillar artery from facial artery
• Lingual vein
• Anterior 2/3rds drain into submental and submandibular nodes –> deep cervical lymph nodes
• Posterior 1/3 –> deep cervical lymph nodes

Question 62

Thyroid

Answer 62

• Anterior neck, spans C5-T1
• 2 lobes, central anterior isthmus - “butterfly-shape”
• Wrap around cricoid cartilage and superior rings of trachea
• Bound by pretracheal fascia

Relations
* Anterior - infrahyoid muscles, superior belly of omohyoid and sternohyoid
* Lateral - carotid sheath (common carotid, IJV, CN X)
* Medial - larynx, pharynx, trachea, oesophagus, external laryngeal and recurrent laryngeal nerves

Vasculature
* Superior thyroid artery (external carotid)
* Inferior thyroid artery (thyrocervical trunk, branch of subclavian)
* ~10% thyroid ima artery (from brachiocephalic trunk)
* Superior, middle and inferior thyroid veins form a venous plexus
* Superior and middle veins –> IJV
* Inferior –> brachiocephalic

Innervation
* Branches derived from the sympathetic trunk
* Release of hormones regulated by pituitary

Lymphatic drainage
* Paratracheal
* Deep cervical

Question 63

Transversus abdominis plane (+ block)

Answer 63

• Facial plane superficial to the transversus abdominis muscle (innermost layer of the anterolateral abdominal wall)
• Upper fibrous anterior part of the muscle lies posterior to the rectur abdominis muscle and reaches the xiphoid process
• Posterior aponeurosies of the transversus abdominis and internal oblique muscles fuse and attach to the thoracolumbar fascia
• Intercostal, subcostal and L1 segmental nerves communicate to form the upper and lower TAP plexuses which innervate the anterolateral abdominal wall, including the parietal peritoneum

Performing the Block
* Prerequisites - consent, monitoring, IV access, trained assistant, equipment, emergency drugs
* Skin cleaning
* Prep-stop-block
* Position - supine, wedge under ipsilateral hip
* Probe placed in the axial plan on the midaxillary line between the subcostal margin and the iliac crest
* Target is the fascial plane between the internal oblique and transversus abdominis muscles, approximately in the midaxillary line
* Volume at least 15ml, high volume blocks

Question 64

Trigeminal

CN V

Answer 64

• Mesencephalic, principal sensory and spinal nuclei of trigeminal nerve - 3x sensory nuclei
• Motor nucleus of the trigeminal nerve
• Extend from midbrain to medulla
• At the pons - sensory nuclei merge to form a sensory root
• Motor nucleus continues to form a motor root
• Middle cranial fossa - sensory root expands into the trigeminal ganglion, located lateral to the cavernous sinus, in a depression of the temporal bone
• Superior cerebellar artery passes through this trigeminal cave/Meckel’s cave
• Peripheral aspect of the trigeminal ganglion gives rise to 3 divisions
  – V1 - ophthalmic
  – V2 - maxillary
  – V3 - mandibular
• Motor root passes along the floor of the trigeminal cave, its fibres are only distributed to the mandibular division

V1
* supraorbital nerve
* supratrchlear nerve
* intratrachlear nerve
* passes through supraorbital fissure to provide frontal and lacrimal branches, 3rd branch divides to short and long nasociliary nerves and anterior and posterior ethmoidal nerves

V2
* through foramen rotundum then divides into 2
* upper branch divides into 3
– zygomaticotemporal
– zygomaticofacial
– infraorbital
* lower branch forms the sphenopalatine ganglion then divides into 3
– greater palatine
– lesser palatine
– nasopalatine

V3
* passes through the foramen ovale then divides into 5 branches
– auriculotemporal
– lingual
– inferior alveolar
– buccal
– nerve to mylohyoid

Question 65

Nervous Supply of the Upper Limb

Answer 65

Osteotomes
* Head of humerus - axillary nerve
* Shaft of humerus - radial and musculocutaneous
* Distal humerus - radial and median
* Radius - radial and median
* Ulnar - median and radial
* Carpals - median and radial
* Metacarpals - median, radial and ulnar
* Phalanges - median, radial and ulnar

Myotomes
* C5 - biceps (bends elbows)
* C6 - deltoids, extensor carpii (bends wrist back)
* C7 - triceps (straightens elbows)
* C8 - palmar interossei (bends fingers)
* T1 - dorsal interossei (spreads fingers)

Sensory innervation
* Ulnar - ulnar aspect of hand, little and 1/2 of ring finger
* Median - radial aspect of hand, thumb + 2.5 fingers + finger tips
* Radial - posterior hand and arm
* Medial cutaneous nerve of forearm - ulnar aspect of forearm, across cubital fossa and anterior aspect of upper arm
* Medial cutaneous nerve of arm - small area of inner upper arm
* Intercostobrachial - small area of inner upper arm
* Lateral cutaneous nerve of forearm - radial aspect of forearm, to above elbow
* Axillary - regimental badge area
* Supraclavicular - anterior and lateral shoulder
* Suprascapular - posterior shoulder

Dermatomes
* T10 - umbilicus
* T6 - xiphoid process
* T4 - nipples
* T2 - armpit
* T1 - inside of upper arm to below the elbow
* C8 - little finger + ulnar aspect of half of forearm
* C7 - ring finger + middle finger
* C6 - thumb and index finger + radial aspect of forearm to above the elbow
* C5 - outer aspect of upper arm
* C4 - shoulder
* C2 - back of head

Question 66

Vagus Nerve

Answer 66

• Cranial nerve X
• Sensory - innervates the skin of the external acoustic meatus and the internal surfaces of the laryngopharynx and larynx. Provides visceral sensation to the heart and abdominal viscera
• Special sensory - tast sensation to the epiglottis and root of the tongue
• Motor - majority of muscles of the pharynx, palatoglossus, soft palate and larynx
• Parasympathetic - smooth muscle of trache, bronchi, GI tract and regulates heart rhythm

Anatomical course
* Originates from the medulla of the brainstem
* Exits cranium via the jugular foramen (with CN IX and XI)
– auricular branch arises within the cranium (sensation to posterior part of the external auditory canal and external ear)
* Travels inferiorly with the IJV and common carotid artery in the carotid sheath
* Right vagus - anterior to SC artery, posterior to sternoclavicular joint, entering thorax behind the lung hila
* Left vagus - inferiorly between L common carotid and L SC artery, posterior to the sternoclavicular joint, entering thorax behind the lung hila
– pharyngeal branch arises in the neck (motor innervation to the majority of muscles of the pharynx and soft palate)
– superior laryngeal nerve - internal (sensory innervation to the laryngopharynx and superior part of the larynx)
– superior laryngeal nerve - external (cricothyroid muscle of the larynx)
– right recurrent laryngeal nerve (majority of intrinsic muscles of the larynx)
* Right vagus nerve forms the posterior vagal trunk
* Left vagus nerve forms the anterior vagal trunk
– left recurrent larnyngeal nerve (majority of intrinsic muscles of the larynx)
– cardiac branches (regulate HR and provide visceral sensation to the heart)
* Vagal trunks contribute to the formation of the oesophageal plexus (smooth muscle of oesophagus)
* Vagal trunks enter the abdomen via the oesophageal hiatus (T10)
* Terminate in the abdomen by dividing into branches that supply the oesophagus, stomach and the small and large bowel (up to the splenic flexure)

Question 67

Venous drainage of the lower limb

Answer 67

Drained by deep and superficial veins.

Deep Veins
- underneath the deep fascia
- run with the arteries (usually within the same vascular sheath)
- dorsal venous arch —> some veins penetrate deep into the leg, forming the anterior tibial vein
- medial and lateral plantar veins combine to form the posterior tibial and fibular veins
- anterior tibial, posterior tibial and fibular veins unit to form the popliteal vein behind the knee
- popliteal vein enters the thigh via the adductor canal —> femoral vein (accompanies femoral artery)
- deep vein of the thigh (profound a femoris vein) drains blood from the thigh muscles via perforating veins into the distal section of the femoral vein
- femoral vein leaves the thigh by running underneath the inguinal ligament —> external iliac vein
- gluteal region drained by inferior and superior gluteal veins —> internal iliac vein

Superficial Veins
- in the subcutaneous tissue
- draining into the deep veins
- great saphenous vein formed by dorsal venous arch of the foot and dorsal vein of the great toe
- ascends up the medial side of the leg, passing anteriorly to the medial malleolus at the ankle and posteriorly to the medial condyle at the knee
- receives tributaries from other small superficial veins
- drains into the femoral vein immediately inferior to the infant ligament
- small saphenous vein formed by the dorsal venous arch of the foot and dorsal vein of the little toe
- moves up the posterior side of the leg, passing posteriorly to the lateral malleolus, along the border of the gastrocnemius muscle
- empties into the popliteal vein in the popliteal fossa

Question 68

Venous drainage of the upper limb

Answer 68

• Subclavian vein
  – cephalic vein (lateral)
  – basilic vein (medial)
• Deep and superficial palmar arches
• Median cubital vein of the forearm –> basilic vein
• Median cubital vein joins the basilic and cephalic veins together

Question 69

Wrist Anatomy

Answer 69

• 7 lines of the wrist (from lateral to medial on volar aspect)
  – radial artery
  – flexor carpi radialis
  – median nerve
  – palmaris longus
  – ulnar artery
  – ulnar nerve
  – flexor carpi ulnaris
• Nerves are deep compared to the tendons
• 1st 4 superior to radius, last 3 superior to ulnar

Wrist bones (from lateral to medial)
* trapezium
* trapezoid
* capitate
* hamate
* scaphoid
* lunate
* triquetrum
* pisiform