Large Intestine
The large intestine consists of the appendix, caecum, colon, rectum and anal canal. The colon subdivides into the ascending colon, transverse colon, descending colon and sigmoid colon. Neither the villi nor the plicae circulares are present in the mucosa of the large intestine; however, the lamina propria houses crypts of Lieberkuhn. In addition, the large intestine does not possess Paneth cells, with the possible exception of the appendix. The outer longitudinal layer of the muscularis externa of the colon presents three thickened, equally spaced bands known as teniae coli. Between the teniae there are sacculations known as haustra that are present on the external surface of the caecum and colon. Additionally, the serosa of the large intestine has small fatty projections known as mental appendices.
I. Colon
a. Mucosa The mucosa of the colon possesses folds thinner than that of the small intestine. The mucosal epithelium of the large intestine contains the same cell types found in the small intestine except Paneth cells.
b.Submucosa The submucosa of the colon resembles that of the small intestine, and it presents spiral folds, plicae circulares (valves of Kerckring). c. Muscularis Externa The muscularis externa of the colon is composed of two smooth muscle layers: inner circular and outer longitudinal. The outer longitudinal layer presents teniae coli. They are composed of smooth muscle longitudinally arranged in three flat ribbons. Teniae coli function is formation of haustra coli (sacculations). Auerbach’s plexus lies between the two smooth muscle layers. As in the small intestine, two types of muscle contraction are produced by the muscularis externa of the large interstine: segmentation and peristalsis. d.Serosa The caecum and transverse colon are covered by a serosa, whereas the ascending and descending colon are covered by an adventitia. The serosa presents the appendices epiploicae, small, fat-filled pouches. II. Cecum
The cecum is a blind pouch found just distal to the ileocecal valve. It has histological features similar to those of the colon. |
Histology Text: Oesophagus - Stomach - Small Intestine - Appendix - Rectum & Anal Canal
Histology Atlas - Histopathology - Histology Quiz
Histology Atlas - Histopathology - Histology Quiz