2. Introduction
• Mainly intraperitoneal organ
• Develops from distal foregut
and midgut
• Extends from pylorus to the
ileocecal junction
• Subdivided into:
• Duodenum
• Jejunum
• Ileum
3. Function
• Enzymatic breakdown of chyme into
monosaccharides, amino acids, and fatty acids
(predominantly in the duodenum)
• Absorption of nutrients and water (predominantly in
the jejunum and ileum)
• Innate immune system and adaptive immune system
function
4. Anatomical subdivisions
• First and widest part of the
small intestine
• C-shaped: surrounds the
head of the pancreas
• Located mainly within the
epigastric and umbilical
regions of the abdomen
• Only the 1st part of the
duodenum is
intraperitoneal. The 2nd–4th
parts are retroperitoneal.
Duodenum
5. Duodenum
• Parts of the duodenum:
• Superior
• Descending
• Horizontal
• Ascending
6. Descending part
• Minor duodenal papilla
• Opening of the
accessory duct of
pancreas
• Major duodenal papilla
• Opening of the Ampulla
of Vater
• Forms sphincter of
Oddi
8. Mucosa
• Transverse folds of
mucosa - the plicae
circulares.
• The smaller mucosal
folds are intestinal villi
9.
10. Jejunum and Ileum
• Jejunum
• Second part of the small
intestine
• Located mainly in the LUQ
of the abdomen
Intraperitoneal
• Ileum
• Final and narrowest part of the small
intestine
• Located mainly in the RLQ of the abdomen
• Intraperitoneal
• Separated from the large intestine at the
ileocecal junction by the ileocecal valve:
• Muscular sphincter that regulates the
passage of fluid and nutrients from the
ileum into the cecum and prohibits
reflux
• Provides a mechanical barrier to
bacterial migration into the small
intestine
11. Arterial Blood Supply
• Duodenum
• Gastroduodenal
• Superior
Pancreaticoduodenal
• Inferior
Pancreaticoduodenal
• Jejunal
• Branches of the superior
mesenteric artery →
intermesenteric arterial
anastomoses → vasa recta
• Ileum
• Ileal branches of the
superior mesenteric artery
→ intermesenteric arterial
anastomoses → vasa recta
