Small intestine anatomy

Duodenum 4 parts: 

• Wraps around head of pancreas
• Supplied by celiac trunk, SMA, sup, mid & inferior pancreaticoduodenal artery 

1st part - superior

• only intraperitoneal part 
• hepatoduodenal ligament + greater omentum attachment 

2nd part - descending

• contains major (+ minor) duodenal papilla
  • hepatopancreatic sphincter 

3rd part - transverse, 4th ascending

• 4th part forms duodenojejunal flexure 
• this flexure attachment to the posterior abdominal wall via ligament of Treitz

Jejunum

• entirely intraperitoneal
• no clear line between jej. + ileum ~2/3 of continuem 
• lots of branches of SMA
• wall of jejunum is thicker and lumen wider
• jejunum contains more prominent circular folds of Kerckring