Download CH23_Anatomy_of_the_Large_Intestine

CH 23
Anatomy of the
Large Intestine
James F. Thompson, Ph.D.
Large Intestine
 Functions
 Completion of nutrient
absorption, especially
the final absorption of
H2 O
 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
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
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)
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
General Histology of GI Tract
 Same histological organization from inside to outside
and from end to end
Large Intestine: Histology
 No villi or permanent
circular folds in
mucosa
 Long thin intestinal
glands
 Columnar cells with
microvilli for
absortption
 Solitary lymphatic
nodules
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
Large Intestine: Histology
Colonoscopy
diverticula
fecaltih
normal
Colon Polyps
End CH 23
Anatomy of the
Large Intestine