1. Anatomy of the Large Intestine
CH 23
Anatomy of the
Large Intestine
James F. Thompson, Ph.D.

2. Large Intestine Functions Anatomy
Completion of nutrient absorption, especially the final absorption of H2O
Intestinal normal flora manufacture certain vitamins (B complex, K)
Formation and expulsion of feces
Anatomy
1.5 m L, 6.5 cm W
Divided into 4 general areas:
cecum
colon
rectum
anal canal

3. Large Intestine: Anatomy
Ileum to cecum -
ileocecal sphincter
cecum hangs below valve with appendix
appendix vestigial
Open end of cecum merges with a long tube, the colon (4 subdivisions):
ascending
transverse
descending
sigmoid

4. Large Intestine: Anatomy
Rectum
last 20 cm of GI tract, terminal 2-3 cm = anal canal
rectal valves for flatus (gas)
anal columns – stratified squamous epithelium
anal sinuses – mucus secretion
Anus
external opening
internal sphincter of smooth muscle (involuntary)
external sphincter of skeletal muscle (voluntary)

5. Large Intestine Anatomy (cont.)
Longitudinal smooth muscle reduced to bands: teniae coli
Teniae coli contractions create pouches in the large intestine called haustra
Circular smooth muscle contraction in the walls of the haustra compact the feces and assist in reabsorption of water and electrolytes

6. General Histology of GI Tract
Same histological organization from inside to outside and from end to end

7. Large Intestine: Histology
No villi or permanent circular folds in mucosa
Long thin intestinal glands
Columnar cells with microvilli for absortption
Solitary lymphatic nodules

8. Large Intestine: Histology
Muscularis mucosa
Longitudinal and circular smooth muscle layers
Longitudinal muscles reduced to longitudinal bands (teniae coli) which compress the large intestine into haustra (pouches)
Serosal part of visceral peritoneum
Small pouches of peritoneum
Filled with fat (epiploic appendages) attached to teniae coli

9. Large Intestine: Histology

10. Colonoscopy
diverticula
fecaltih
normal

11. Colon Polyps

12. End CH 23 Anatomy of the Large Intestine