the intestines

  1. duodenum: (25 cm)
    • retroperitoneal
    • C‑shaped, enclosing the head of the pancreas
    • receives the bile and pancreatic ducts via the duodenal ampulla
  2. jejunum (2.5m) and ileum (3.5m):
    fan‑shaped mesentery (mesentery proper)
  3. blood supply and venous drainage:
    • mainly superior mesenteric artery from abdominal aorta
    • superior mesenteric vein drains into the portal vein
  4. mucosa:
    • plicae circulares: permanent transverse folds
    • epithelium: simple columnar epitheliummostly absorptive cells whose luminal surfaces bear microvilli (brush border)between absorptive cells are goblet cells
    • intestinal glands (crypts of Lieberkuhn)‑ between the bases of the villi: absorptive and goblet cells
  5. mucosa:
    • 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
    • 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)
  6. submucosa:
    in the duodenum contains duodenal (Brunner's) glands that secrete alkaline mucus
  7. Large Intestine:
    • 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:
    • superior mesenteric artery: cecum, ascending and transverse colon
    • inferior mesenteric artery: descending and sigmoid colon; rectum
    • corresponding veins drain to the portal vein
  12. 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. 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
the intestines
lecture 20