small bowel Flashcards
Gut embryology
https://www.youtube.com/watch?v=vJA1A0v6Aa4
Small intestine is derived from..?
Midgut. (With the exception of proximal duodenum, which is deriv from foregut)
Meckel’s diverticulum is vestige of what?
Vitelline duct, which joins the yolk sac at the junction of the cranial and caudal limbs of the midgut limb
How long is the small bowel?
5-10 m (longest organ in GI tract)
Ligament of Treitz marks
Junction of duodenum and jejunum
Plicae circulares
Transverse mucosal folds in the lumen of the small bowell- present in distal duodenum and jejunum
Blood supply to duodenum
Proximal: gastroduodenal artery (off of proper hepatic artery-> branches into ant superior and post superior pancreaticoduodenal arteries).
Distal: inferior pancreaticoduodenal artery (off of SMA -> branches into ant inferior and post inferior pancreaticoduodenal arteries)
Venous drainage of duodenum
Ant and post pancreaticoduodenal veins -> SMV -> splenic vein + SMV = portal vein
Blood supply of jejunum and ileum
Branches of the SMA
Summary of small bowel blood supply
All of small bowel is supplied by branches of the SMA except the proximal duodenum, which is supplied by branches off the celiac trunk
Lymphatic drainage of small bowel
-> mesenteric nodes -> LN channels -> cisterna chyli (btw aorta and IVC) -> thoracic duct -> left subclavian vein
Innervation to small bowel
Sympathetic: vagus and celiac ganglia
Parasympathetic: plexus at base of SMA
Enteric NS: myenteric plexus = Meissner plexus (base of submucosa) and Auerbach plexus (in btw inner circumferential and outer longitudinal muscle layers)
What vessel is at risk of erosion/bleed if posterior duodenal bulb ulcer perfs?
Gastroduodenal artery
How to tell between jejunum and ileum?
Jejunum has few arcades with loong vasa recta, while ileum has many arcades with short vasa recta
Gastrin
Released in antrum. Stimulates gastric acid secretion and cell growth. Stimulated by vagus, food in Antrum, gastric distention, calcium. Inhibited by antrum pH
Cholecystokinin (CCK)
Released in the duodenum. Action is gallbladder contraction, inhibit gastric emptying. Stimulated by proteins and amino acids, fat, and acid. Inhibited by trypsin and chymotrypsin.
Secretin
Released in the duodenum. Action is to cause pancreas to stimulate bicarb, stimulates pepsin secretion, inhibits gastric acid secretion. Stimulated by low pH and duodenal fat. Inhibited by high duodenal pH.
Somatostatin
Released from pancreas. Action is to increase small bowel absorption of water and electrolytes, inhibits GI motility, secretion/action of all GI hormones. Stimulated by intraluminal fat, catecholamines. Inhibited by acetylcholine.