Anatomy Flashcards
Describe the anatomy and branches of Brachial plexus
Brachial plexus is made of anterior division of C5 - T1 spinal nerves. It has roots, trunks, divisions, cords and brances (Read The Damn Comic Book)
These Roots lie between the scalenus medius and scalenus anterior
Roots form 3 trunks which lie in the posterior triangle. Superior trunk forms from C5C6, Middle trunk from C7 and inferior trunk from C8T1
Trunks from anterior and posterior divisions behind the clavicle
Divisions form cords around the second part of the axillary artery (cords are named accordign to their position around axillary artery).
Lateral cord - Ant div of superior and middle trunks
Posterior cord - Posterior divisions of sup, middle and inf trunks
Medial trunk - ant div of inf trunk
Branches:
From Roots:
- Dorsal Scapular Nerve (c5)
- Nerve to subclavius C5,6
- Long thoracic nerve C5,6,7 (serratus anterior)
From Trunks:
- Suprascapular nerve C5,6
From Cords:
- Lateral Cord (MLL)
- Musculocutaneous nerve
- Lateral pectoral nerve
- Lateral root of median nerve
- Posterior cord (ULTRA)
- Upper and lower subscapualr nerve
- Thoracodorsal nerve
- Radial nerve
- Axillary nerve
- Medial cord (MMMMU)
- Medial pectoral nerve
- Medial cutaneous nv of arm
- Medial cutaneous nv of forearm
- Medial root of median nerve
- Ulnar nerve
Branches of axillary artery
The three parts of the axillary artery are divided by the relationship to pectoralis minor.
- The first part (above pec. minor)
- The superior thoracic artery
- The second part (behind pec. minor)
- The Thoracoacromial artery
- Clavicular
- Deltoid
- Acromial
- Pectoral
- The lateral thoracic artery
- The Thoracoacromial artery
- The third part (below pec. minor)
- The subscapular artery (largest br.)
- Gives off circumflex scapular to become thoracodorsal artery
- The anterior circumflex humeral artery
- The posterior circumflex humeral artery (passes through quadrangular space with axillary nerve)
- The subscapular artery (largest br.)
Describe the course of the phrenic nerve
Describe the ligaments of liver
the liver has 7 ligaments
- coronary ligaments (left and right) - these are peritoneal reflections from the dipgram to the liver. They have an anterior (sup) and posterior (inferior layer that split on the right side to demarcate the bare area of the liver. Medially they are contimous with the faciform ligament
- Trianlgular ligaments (l and R) - extreme lateral end of the coronary ligaments - attached to the diaphragm
- Falciform ligament - From the anterior abd wall to the anterior leaf of coronary ligamnets
- Ligamentum teres - free lower edge of the falciform ligament. Contains the obliterated left umbo vein (drains bllod to the left branch of portal V)
- Ligamnetum Venosum - denoted the obliterated ductus venosus that connects left portal vein to left hepatic vein to bypass liver. Posterior surfce of liver connecting the porta to the left hepatic vein
- Gastrohepatic ligamnet part of the lesser omentum
- Hepatoduodenal ligament - part of lesser omentum
branches of femoral artery in groin
- Superficial circ iliac
- superficial epigastric
- Superficial external pudendal
- deep internal pud
terminal branches - SFA and profunda
What are the boundaries of the ischianal (ischiorectal fossa)? What are the contents?
Anteriorly
- fascia covering transversus perineii superficialis
Posteriorly
- Gluteus Max
- Sacrotuberous ligament
Superiorly
- Levator Ani
Inferiorly
- Skin
Medially
- Levator ani
- external sphincter complex
- corrugator custis ani
Laterally
- Obturator interus with overlying fascia
- Ischial tuberosity
Contents
- Fibrofatty tissue
- Inside Alcock’s canal
- Pudendal nerve, art, vein
- Outside Alcock’s canal
- Inferior rectal nerve artery vein
What is the blood supply of the breast
4 sources:
perforating branches of IMA
perf. branches of post. intercoastal
pectoral branch of thoracoacromial
branches of lateral thoracic
relations of pyriformis
Superior
- sup gluteal nv and vesses
Inferior
- Inf gluteal nv and vs
- Pudendal nv and int pud vs
- post fem cutaneous nv
- Sciatic nv
Anterior
- scaral plexus
what are the usual layers of the GI tract
Mucosa
- epithelium
- lamina propria
- Muscularis mucosae
Submucosa
Muscularis Propria
- inner circular
- outer longitudinal
Serosa
Describe the fascial layers of neck
The neck is enclosed in superficial fascia, deep to whihc lies the deep fascia.
SUPERFICIAL - superficial fascia of neck lies deep to the subcutaneous tissue and encloses the entire neck and contains the platysma.
DEEP FASCIA - has three logitudinal columns that run alon the length of the neck
- Superficial (investing) layer - starts at nuchal line and splits to enclose the trapezius, SCM, straps, parotid and SMG.
- Middle layer - encloses the viscera - larynx, trachea, pharynx, esophagus, thyroid and parathyroids. The anterior and posterior parts of this is also called the pre-tracheal and buccopharyngela fascia
- Deep layer - also called pre-verterbral fascia. This encloses the spine and all its muscles. It has
- an anterior ALAR fascia (between the buccopharyngeal and pre-vertebral fascia)
- Posterior PREVERTEBRAL fascia that lies immidietly anterior to the vertebrae.
- CAROTID SHEATH - all 3 layers of the deep fascia contribute to form the carotid sheath.
describe the important surgical spaces of neck for infection
The relevant spaces are
- submandibular space -
- parapharyngeal space
- Retropharyngeal space
- True retropharyngeal space (danger space)
- pre-vertebral space
SUBMANDIBULAR
- Between floor of mouth and investing fascia over SMG
- myleohyoid divides this into sublingual and submyelohyiod spaces
- continous laterally with parapharyngeal space
- involved in Ludwigs angina
Parapharyngeal space
- inverted cone lateral to pharynx with base on base of skull and tip on hyoid
- Styloid process (and its muscles) divide this into anterior (nothing) and posterior (IX,X,XI,XII nvs)
- communicates medially with submandibular space
Retropharyngeal space
- True - between buccopharyngeal pfascia and alar fascia
- Extends to the mediastinum and communicates on 2 sides allowing infection to track (danger space)
- Pre-vertebral space - between alar and pre-vertebral fascia.
Discuss midgut embryology
Midgut embryology is all about the physiological hernia and the reduction thereof by rotation around the SMA-axis. Vitelline duct remnants give rise to a Meckel’s diverticulum.
- The primary intestinal loop enters the extra-embryonic coelom in the umbilical cord in the 6th week.
- Rotation is 270⁰in an anti-clockwise direction (from superior to right to left of the fetus, of which 90 occurs outside the body and 180 occurs inside) and as a result:
- The duodenum passes to the left under the SMA
- The transverse colon sits anterior to everything else
- The caecum ends up in the RIF.
- Return of the gut occurs in a craniocaudal sequence- the cranialmost part returns first.
- Malrotation causes problems with the duodenum/SMA relationship and the position of the caecum & appendix
- The physiological hernia reduces due to
- Normal growth and expansion of the abdominal cavity
- Reduced growth of the liver
- Regression of the mesonephroi
- Vitelline duct remnants form a Meckel’s diverticulum with/without a band or fistula. Meckel’s are found two feet from the IC-valve in 2% of people.
- Omphalocele is failure of reduction of the physiological hernia
- Duplication cysts are usually on the mesenteric side of the intestine and may contain aberrant mucosa.
- Intestinal atresia and stenosis are usually due to vascular accidents. With duodenal atresia consider Down’s syndrome.
What are the layers of the primitive embryo and what do they develop into
Ectoderm develops into the skin and CNS
Mesoderm has 3 parts (medial to lateral)
- Paraaxial mesoderm - gives rise to the somites (Muscles, bones, cartilage)
- Intermediate mesoderm - gonads and kidneys
- Lateral plate - has 2 layers
- Parietal (somatic lateral plate - parietal peritoneum, blood vessels
- Viseceral / splanchnic plate - visceral peritoneum, stroma and muscles of gut
- Endoderm - epithelium, parenchyma of GIT
What are the parts of the embryonic gut
The embryonic gut has 4 parts
- Pharyngeal gut - from mouth to the respiratory diverticulum
- Foregut - resp diverticulum to liver bud
- Mid gut - liver bud - junction of prox2/3 and distal 1/3 of tranverse colon
- Hind gut - distal transverse colon to cloacal membrane
Development of stomach and duodenum
Stomach develops from the primitive fore gut and undergoes 3 critical steps (starting around week 4) to get its final shape and lie:
- it rotates 90 degrees to the right (clockwise when viewed from top) on its longitudinal axis (this creates the lesser sac)
- the posterior wall grows more rapidly than the anterior wall giving rise to the greater and the lesser curves
- Finally it rotates slightly clockwise along it’s longitudinal axis to have an oblique lie.
Duodenum (and Pancreas) are also pulled into the the same rotation by the stomach. This gives rise to the C shape of the duodenum and makes the pancreas a retroperitoneal organ. The duodenum undergoes temporary epithelial obliteration but the lumen re-canalises by the 8th week.
Discuss hindgut embryology
- The terminal hindgut enters the cloaca from which the bladder and urethra also form. The cloacal membrane near the proctodeum separates the ectoderm from the endorderm),
- The primitive cloaca connects with the allantois, the hindgut and the mesonephros
- The urorectal septum grows to join the cloacal membrane thereby separating the cloaca in a urogenital sinus and anorectal canal.
- The place where the urorectal septum meets the clocal membrane becomes the perneal body.
- The anal membrane ruptures in the 9th week.
- The upper part of the anal canal is endodermal in origin, but the lower third is ectodermal. The junction between them is the pectinate line.
- Imperforate anus is caused by non-perforation of the anal membrane or deviation of the urorectal septum posteriorly. Fistulas occur commonly in this condition and open on the perineum, vagina or urethra.
What are the types of esophageal atresia
- Esophagus elongates as the embryo grows
- The tracheo-bronchial bud comes off the esophagus and gradually gets separated by development of the tracheo-esophageal spetum.
- Abnormal development of thi septum can cause esophageal atresias with(out) fistula
- Atresia with no fistula (complete atresia or stenosis of esophageal lumen)
- Proximal fistula, distal atresia
- Distal fistula promimal atresia (commonest 84%, causes polyhydramnios)
- Both proximal and distal fistula
- H-shaped fistua
What are the derivatives of the pharyngeal pouches?
These pouches are lined by endoderm and gives rise to many things:
First pouch:
- This forms a stalk-from the fourth arch - like diverticulum, the tubotympanic recess, that becomes the Eustachian tube and middle ear cavity. It comes close to the first pharyngeal cleft, only separated by the tympanic membrane.
Second pouch:
- This forms the palatine tonsil in the tonsillar fossa. That’s why branchial cysts -of second cleft origin – may have a fistulous process that ends in the tonsillar fossa – of second pouch origin.
Third pouch:
- Gives rise to the inferior parathyroid gland and the thymus. These parathyroids have a long way to migrate and can therefore end up anywhere (thyroid, mediastinum)
Fourth pouch:
- Gives rise to the superior parathyroid gland. This has a much shorter route of migration so less likely to be ‘lost’.
Fifth pouch:
- Gives rise to the ultimobranchial body that incorporates into the thyroid gland and gives rise to the C-cells that secrete calcitonin. Medullary thyroid cancer originates in this body (hence calcitonin is its tumour marker).
- Proliferation of mesenchyme in the second arch cause it to overgrow/overlap the third and fourth arches. The second arch mesenchyme then fuses with the epicardial ridge in the lower part of the neck. Clefts 2,3 and 4 therefore ‘loses’ their connection with the outside world. When this ‘overgrowth’ is not complete, the clefts of 2,3,or 4 may remain in contact with the outside and form a branchial fistula. If ectoderm from clefts 2,3 or 4 remain after the ‘overgrowth’ of the second arch, a branchial cyst may form, characteristically under the anterior border of sternocleidomastoid. Rarely the cyst will connect the second cledt with the second pouch – a branchial fistula with internal fistula tract to the tonsillar fossa.*
Describe the embryology of tongue
- From the first pharyngeal arch, on the inside, develops two lateral lingual swellings and a median tuberculum impar.
- A second median swelling, the copula, is formed by mesoderm of the 2nd, 3rd and 4th arches on the inside
- A third median swelling originates from the fourth arch – this is the epiglottic swelling
- Behind the epiglottic swelling is the laryngeal orifice (the tracheobronchial diverticulum) flanked by the arytenoid cartilages.
- The lateral lingual swellings overgrow the tuberculum impar and becomes the anterior two-thirds or body of the tongue. This lingual tissue is invaded by the occipital somites, supplied by the hypoglossal nerve. Therefore the motor supply of the tongue is XII and the sensory supply is lingual and chorda tympani nerves (of V3, the nerve of the first arch. The chorda tympani only hitch-hikes along VII).
- The posterior part of the tongue is mainly from third arch mesoderm, hence supplied by the glossopharyngeal nerve (IX)
- The epiglottis is supplied by the superior laryngeal nerve, the nerve of the fourth arch
