Lower GI Tract Flashcards
Segments of Small Intestine
Duodenum, Jejunum, Ilieum
Segments of Large Intestine
Colon, Rectum, Anus
Barriers of the Dueodenum
Begins - Distal to the pylorus of the stomach
Ends - at the Dueodenojejunal Junction
Duodenum
(shape and divisions)
- C-shape around the head of the pancreas
- divided into four parts
- sections 2-4 are secondarily retroperitoneal
1st Part of the Duodenum
- only part that has a mesentary (peritoneal) - all other sections are secondarily retroperitoneal
- part of the foregut
2nd/Descending Part of Duodenum
- where the common bile ducts and pancreatic duct dram into the duodenum
- drain through the major dueodenal papilla (of Vater)
3rd Part of Duodenum
- travels horizontally POSTERIOR to the SMVs
4th Part of Duodenum
- ascends until junction with the jejunum
Ligament of Treitz
- suspensory muscle/ligament of the duodenum at the duodenojejunal junction
Duodenal Blood Supply
1st Portion - Celiac Axis (Foregut): Gastroduodenal and Superior Pancreaticoduodenal Arteries
Distal to Hepatoduodenal Ligament (Midgut) - Superior Mesenteric Artery and Inferior Pancreaticoduodenal Arteries
Jejunum and Ilium
- remainder of the small intestine
- gradual transition, no clear demarcation
Ilium = proximal
Jejunum = distal
Jejunal and Ilium Mesentary
- contains blood supply, nerves, and lympatics between two layers of visceral peritoneum
~15cm long and runs obliquely from the duodenojejunal junction to the ileocecal valve
- attached to the posterior abdominal wall
Jejunum vs. Ileum Mesentary Blood Supply
Jejunum:
- longer vasa recta
- fewer vascular arcades
- more capillaries (bc more absorption)
Ilium:
- shorter vasa
- more vascular arcades
Efferent (motor) Nerve Supply to Small Intestines
Autonomic:
- Sympathetics -*
- Pre-ganglionic Thoracic Splanchnic Nerves
- Synapse in the Preatortic Ganglia around Celiac Axis and SMA
- Parasymathetics -*
- Pre-ganglionic travel in Vagus Nerve (CN X)
Peritoneal Gutters
- created by the attachments of the mesenteries
- one on either side of ascending and descending colon
**medial ascending colon gutter WILL NOT drain directly into the pelvic cavity because blocked by small bowel mesentery
Plicae Circulares
- mucosal folds of the small bowel
- most prominent in jejunum and gradually decrease as go towards ilium
Plicae Semilunares
- more widely spaced plicae/folds in the colon that do not completely incircle the lumen