Anatomy Flashcards
L3.1 Describe the development of the gut tube and the derivatives of the embryonic foregut, midgut, and hindgut
Primordial gut: developed from dorsal part of yolk sac within embryonic disc.
- epithelial lining & glands: yolk sac endoderm
- smooth muscle & CT: splanchnic mesoderm
- splits into 3 parts:
1. foregut:
- pharynx and deriv.
- lower resp. tract
- esophagus & stomach
- liver & biliary apparatus
- pancreas
- proximal 1/2 duodenum (before major biliary apparatus)
2. midgut
- distal 1/2 duodenum
- jejunum & ileum
- cecum & appendix
- ascending colon
- right 2/3 of transverse colon
3. hindgut
- left 1/3 of transverse colon
- descending colon
- sigmoid colon & rectum
- anal canal to pectinate line
- urinary bladder and most of urethra
L3.2 Describe the rotation of the foregut and mindgut during development
Development of Stomach:
- distal part of foregut: fusiform dilatation
- posterior surface has faster growth
- clockwise 90* rotation:
- anterior: lesser curvature
- posterior: greater curvature
- left surface: anterior wall
- right surface: posterior wall
Development of Duodenum:
- caudal foregut & cranial midgut
- tranposition from left to right and retroperitoneal with 90* rotation of stomach
Midgut rotation:
- midgut anticlockwise 90* rotation within umbilical cord, around sup. mesenteric artery
- cranial limb on right and caudal on left
- 2nd anticlockwise 90* rotation as midgut returns to abdomen
- cranial return first - central abdomen
- 3rd anticlockwise 90* rotation of viscera
- return of large intestines - right side
- descent of cecum and appendix
L3.3 Decribe the development and clinical picture of duodenal atresia
- complete occlusion of lumen due to failure to recanalize
- presents with immediate vomiting at birth
- double bubble sign
L3.4 Compare & contrast the development and clinical picture of congenital hypertrophic pyloric stenosis vs duodenal stenosis
Congenital Hypertrophic Pyloric Stenosis:
- projectile vomiting, non-bilious
- presents 3 weeks - 5 months after birth
- pyloric mass - olive shaped
- visible gastric peristaltic wave
Duodenal Stenosis:
- partial occlusion of lumen due to incomplete recanalization of lumen
- bilous vomiting, if stenosis distal to bile duct opening
L3.4 Describe the development of the liver and pancreas
Liver & Biliary Apparatus:
- Hepatic diverticulum arises from caudal part of foregut and extends into the spetum transversum
- diverticulum divides into cranial and caudal parts
- cranial: liver
- caudal: gall bladder and cyctic duct
Pancreas:
- development of ventral pancreatic bud and dorsal pancreatic bud
ventral: lower part of head and uncinate process
dorsal: upper part of head, body, and tail
fusion of ventral with dorsal: main pancreatic duct
dorsal: accessory pancreatic duct
L3.5 Describe the embryologic mechanism responsible for formation of annular pancreas and its clinical significance
bifid ventral pancreatic bud that encircle the second part duodenum, causing an obstruction
L4.1 Describe the embryonic process that fails leading to malrotation of the gut
Nonrotation: caudal lims returns first
- small intestines to right
Reversed rotation: midgut loop rotates clockwise
- duodenum ant. to and tranverse to colon which is post. to superior mesenteric artery, which compresses transverse colon
Mixed rotation & volvulus: failure of final 90* anticlockwise rotation
- cecum lies inferior to pyloris and fixed to peritoneal wall by peritoneal bands
- twisting of intestines
L4.2 Describe the fate of omphaloenteric (vitelline) duct.
- normally obliterates
- clinically:
Meckel’s diverticulum:
- finger-like projection of ileum, retention of vitelline duct
- can become infected
- may form cyst
- may form umbilical fistula (patent to umbilicus
L4.3 Describe the importance of the ligamentum venous (venosum) and its significance in fetal circulation
- fibrous remnant of ductus venosus
- ductus venosus: shunts oxygenated blood from placenta to bypass liver and go directly to the heart
L4.4 Describe the mechanism for development of colonic aganglionosis (Hirshsprung’s disease)
Hircshsprung Disease/Congenital Megacolon:
- failure of migration of neural crest cells in weeks 5-7
- aganglionic segment (absense of autonomic ganglia in myenteric plexus); no peristalsis
L4.5 Describe the developmental mechanism of imperforate anus, anal agenesis, anal stenosis, membranous atresia of the anus, rectal agenesis, and anorectal agenesis
Imperforate Anus:
- failure of anal membrane to perforate
Anal Stenosis:
- narrowed anal canal due to slight dorsal deviation of urorectal septum
Membranous Atresia of Anus:
- formation of anal canal and proximal rectum, but no communication between them.
- may connect by fibrous band of tissue
Rectal Agenesis (Atresia):
- abnormal recanalization
Anorectal Agenesis:
- incomplete separation of cloaca by urorectal septum
L14.1 Describe the location of the abdominal sympathetic chain
lateral horn of thoracolumbar spinal cord T1-L2
L14.2 Describe the location of the sympathetic ganglia associated with the abdominal organs
Greater splanchnics: (T5-9) synapses in celiac ganglion
Lesser splanchnics: (T10-11) synapses into aortico-renal ganglion
Least splanchnic: (T12) synapses in the renal plexus
Lumbar splanchnic: (L1-L2) synpases in the intermesenteric and/or superior hypogastric plexus
L14.3 Describe the contributions from the thoracic splanchnic and lumbar nerves to the para- and preaortic sympathetic ganglia.
paravertebral: 3 cervical ganglia, each associated with each ventral ramus
- white and grey rami communicantes
- greater splanchnic (tT5-9)
- lesser splanchnic (T10-11)
preaortic/prevertebral: at the roots of major arteries:
- celiac: celiac ganglion
- superior mesenteric: superior mesenteric ganglion, aorticrenal ganglion
- inferior mesenteric: intermesenteric plexus
- renal: renal plexus
- superior hypogastric plexus
L14.4 Describe the sympathetis, parasympathetic, and sensory innervation of the foregut, midgut, and hindgut
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