GI Anatomy Review Flashcards
3 developmental regions of the GI tract and the respective supplied unpaired arteries
Foregut = celiac trunk
Midgut = superior mesenteric artery
Hindgut = inferior mesenteric artery
What are in each section of the gut tube?
Foregut
- esophagus
- stomach
- pancreas
- liver
- gallbladder
- spleen (not gut tube derived)
- proximal duodenum
Midgut
- distal duodenum
- jejunum
- ileum
- Cecum
- Appendix
- Ascending colon
- proximal 2/3 transverse colon
Hindgut
- distal 1/3 transverse colon
- Descending colon
- sigmoid colon
- rectum
Intraperitoneal parts of the gut tube
Stomach
Proximal 1st part of duodenum
Jejunum
Ileum
Spleen
Gallbladder
Cecum
Transverse and sigmoid colons
Retroperitoneal gut tube organs
Pancreas
Ascending and descending parts of the colon
Kidneys/ureters
Secondarily retroperitoneal organs of the gut tube
Descending and ascending duodenum
Rectum
Ascending and descending colon
What structures run through the the aortic and esophageal hiatus
Aortic = azygos, aorta, thoracic duct, sympathetic trunk
Esophageal = vagus nerve, esophagus
What two systems drain venous blood from abdominal and pelvic viscera
Caval system
- drains inferior ab wall, pelvis, perineum, lower limbs
- IVC -> heart
Portal system
- drains abdominal organs, kidneys, suprarenal glands, digestive tract
- portal vein -> liver -> IVC -> Heart
What are the 4 collateral anastomoses pathways for the Porto-caval system
1) left gastric -> esophageal veins
- portal HTN causes esophageal varices
2) paraumbilical -> epigastric veins
- portal HTN casques gastric varices
3) superior rectal vein -> middle and inferior rectal veins
- portal HTN causes rectal hemorrhoids
4) colic vein -> retroperitoneal vein
- portal HTN causes retroperitoneal ascites (back)
Structural differences between jejunum and ileum
Jejunum
- larger diameter
- thicker walls
- longer vasa recta
- fewer arcades
- less fatty mesentery
- more plicae circulares
- few lymphoid nodules
Ileum - smaller diameter - thin walls - shorter vasa recta - short numerous arcades - fatty mesentary - fewer plicae circularis - peyers patches present -
What innervates the foregut?
Sympathetic = Greater splanchnic nerves from T5-9 that synapse onto the celiac ganglion
Parasympathetic = vagus nerve
What innervates the midgut?
Sympathetic = Dont synapses on sympathetic chains and T10-12 via lesser/least splanchnic nerves
Parasympathetic = vagus nerve
What innervates the hindgut
Sympathetic L1-L2
1) superior to the rectum: doesnt synapse with sympathetic chain and leaves as lumbar splanchnic nerves via inferior mesenteric ganglia
2) inferior to the rectum: synapses with sympathetic chain and then leaves as lumbar and sacral splanchnic nerves
Parasympathetic: pelvic splanchnic nerves (S2-S4)
What is the pectinate line?
Boundary between superior and inferior portions of the anal canal
Superior:
- is viscerally innervated
- derived from hindgut
- blood supplied from IMA (superior rectal)
- drains lymph via internal illiac lymph nodes
- drains veins via portal system
- sympathetics = uses lumbar splanchnic nerves and inferior hypogastric plexus
- parasympathetics = pelvic splanchnic
- visceral afferents use S2-S4 routes
Inferior:
- is somatic innervated
- derived from proctoderm
- supplied by internal ILAs artery (middle/inferior rectal)
- drains venous supply via caval system
- drains lymph via superior inguinal lymph nodes
- innervated by inferior rectal nerve (pudendal nerve)
- is sensative to pain touch and temperature
Definition of mesentery
Fusion of visceral and parietal peritoneum that suspends organs from the posterior ab wall and provides a means for neuro vasculature communication between the organ and body wall
Greater omentum
Fatty peritoneal fold that passes between greater curvature oft he stomach and primal duodenum
- covers transverse colon, jejunum and ileum
considered “policeman of the abdomen” since it can move over to sites of inflammation and adhere, walling off inflammation and isolating it
