Small Intestine

• Longest part of git, from pylorus to ileocecal junction. Primary site of nutrient absorption
• Duodenum 25cm long. C shape around head of pancreas. Begins at pylorus. Ends at duodenojejunal flexure.
• Duodenum is retroperitoneal. Only proximal few cms covered by peritoneum
• Superior part of duodenum ~5cm. Anterolateral to L1. First 2cms has a mesentery. Posterior to liver and gallbladder. Proximal portion attached to hepatoduodenal ligament and greater omentum
• Descending part of duodenum 7-10cms. Right of the IVC. Curves around head of pancreas. Minor and major duodenal papillary on posteromedial wall.
• Inferior (horizontal) part of duodenum. 6-8cms. Level with L3. Passes over IVC and aorta. Superior mesenteric artery and vein pass anteriorly.
• Ascending part of duodenum ~5cms. L2-L4. Runs along aorta to body of pancreas. Duodenojejunal flexure supported by suspensory muscle of duodenum.
• Both celiac trunk and superior mesenteric artery supply the duodenum. Celiac trunk via the gastroduodenal artery and the superior pancreaticoduodenal artery. Superior mesenteric artery via the inferior pancreaticoduodenal artery
• Duodenum. Lymph. Anterior = pancraticoduodenal, pyloric. Posterior = superior mesenteric
• Jejunum 2/5ths SI. Starts at duodenojejunal flexure. Ileum 3/5ths SI length. Indistinct transition bw the two. Ileum ends at ileocecal Junction. Attached to posterior abdominal wall by mesentery
• Jejunum has thicker wall than ileum. J fewer, but longer loops, more visible vasculature. I more short loops, fattier mesentery = less visible vasculature
• Superior mesenteric vein joins splenic to form portal vein
• Lacteals are specialised projections of intestinal mucous membrane. Absorb fat. Drain into 3 sets of lymph nodes; juxta-intestinal, mesenteric and superior central