LARGE INTESTINE

Function: reabsorption of electrolytes and water and elimination of undigested food and waste.

Consist of several anatomical segments: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal.
"Smooth" surface of mucosa.
The outer longitudinal layer of the muscularis externa exhibits three equally spaced bands - teniae coli.
Crypts of Lieberkuhn - straight tubular glands that extend through the full thickness of the mucosa.

Function:

Barrier - separates the lumen of the digestive tract, which is continuous with the environment, from the body of the organism, immunologic barrier.
Secretion large amounts of mucus.

Composition:

Cells:

Function: transport of electrolytes and water from lumen of the intestine to the circulatory system, secretion of glycocalyx.

Function: unicellular mucin-secreting glands.

Location: in the epithelium between the crypts.

Function: "exhausted" goblet cells.

Location: predominantly in the lower portion of the (crypts).

Function: release of hormones and hormone-like secretions.

lamina propria - collagen table - a thick layer of collagen and ground substance just below the surface epithelium, loose connective tissue, blood capillaries, nerves, diffuse lymphatic tissue, lymphatic nodules and aggregated nodules, crypts, pericryptal fibroblast sheath.
muscularis mucosae - relatively thin inner circular and outer longitudinal layers of smooth muscle.

Composition: moderately dense irregular connective tissue, blood vessels, lymphatic vessels, nerve network and ganglion neurons (Meissner's plexus), white adipose tissue.

Function:

Segmentation - local contractions of circular muscle layer for moving contents into contact with the mucosa for absorption.
Peristalsis - largely involves the longitudial muscle layer and moves the intestinal contents distally.

Composition: Two layers of smooth muscle (inner - circular, outer - longitudinal with teniae coli), nerve network and ganglion neurons (Auerbach's plexus).

Composition: simple squamous epithelium - mesothelium, small amount of loose connective tissue, white adipose tissue, large blood vessels, lymphatic vessels, nerve trunks.

Location: in the anal canal extend through the full thickness of the mucosa and submucosa and even into muscularis externa.

Function: mucus secretion.

Composition: branched straight tubular glands with ducts lined with stratified columnar epithelium.