Anatomy Lecture 20

  1. Small Intestine gross anatomy:
    • 3 parts:
    • duodenum
    • jejunum (2.5m)
    • ileum (3.5m)
  2. duodenum:
    • retroperitoneal
    • shortest part (25 cm)
    • C‑shaped, enclosing the head of the pancreas
    • receives the bile and pancreatic ducts via the duodenal
    • ampulla
  3. jejunum (2.5m) and ileum (3.5m):
    fan‑shaped mesentery (mesentery proper)
  4. blood supply and venous drainage to the small intestines:
    • blood supply: mainly superior mesenteric artery from abdominal aorta
    • venous drainage: superior mesenteric vein drains into the portal vein
  5. histology of the small intestine:
    • plicae circulares ‑ permanent transverse folds
    • mucosa:
    • villi ‑ fingerlike projections
    • simple columnar epithelium: mostly absorptive cells whose luminal surfaces bear microvilli (brush border) and between absorptive cells are goblet cells
    • intestinal glands
    • lamina propria: forms a core for each villus which contains blood capillaries and lymphatic capillaries
    • (lacteals) - isolated aggregations of lymphatic tissue in jejunum which become more extensive in the ileum (Peyers' patches)
    • submucosa:
    • in the duodenum contains duodenal (Brunner's) glands that secrete alkaline mucus
  6. intestinal glands (crypts of Lieberkuhn)
    • between the bases of the villi:
    • absorptive and goblet cells
    • Paneth cells: produce lysozyme ‑ antibacterial
    • enteroendocrine cells: produce cholecystokinin (CCK) and secretin
    • stem cells
  7. Large Intestine:
    • 3 parts:
    • cecum:
    • colon:
    • rectum:
  8. cecum:
    • ileocecal valve
    • vermiform appendix
  9. colon:
    • distinctive features: teniae coli, haustra, epiploic appendages
    • ascending colon: retroperitoneal - right colic (hepatic) flexure
    • transverse colon: transverse mesocolon - left colic (splenic) flexure
    • descending colon: retroperitoneal
    • sigmoid colon: sigmoid mesocolon
  10. rectum:
    • anal canal:
    • anal columns
    • internal and external anal sphincters
  11. blood supply and venous drainage of the large intestine:
    • blood supply:
    • superior mesenteric artery- cecum, ascending and transverse colon
    • inferior mesenteric artery- descending and sigmoid colon; rectum
    • venous drainage: corresponding veins drain to the portal vein
  12. histology of the mucosa:
    • no plicae circularis or villi
    • simple columnar epithelium contains the same cells as small intestine
    • goblet cells increase toward the anus
    • in anal canal a change from simple columnar to stratified squamous epithelium
    • intestinal glands (crypts) are deeper
    • accumulations of lymphatic tissue in the lamina propria (and submucosa)
  13. histology of the muscularis externa:
    • in the cecum and colon, the outer longitudinal layer is in three longitudinal bands (teniae coli)
    • in the anal canal, the circular muscle layer thickened as the internal anal sphincter
Card Set
Anatomy Lecture 20