The digestive system part 8

extends from the ileum to the anus. It is attached to the posterior abdominal wall by its mesocolon, which is a double layer of peritoneum

a fold of mucous membrane that guards the opening from the ileum into the large intestine. It allows materials from the small intestine to pass into the large intestine

hanging inferior to the ileocecal valve is a small pouch

attached to the cecum is a twisted coiled tube.  It is also attached to the inferior part of the ileum.

the open end of the cecum merges with this long tube, which is divided into ascending, transverse, descending and sigmoid portions.

ascends on the right side of the abdomen, reaches the inferior surface of the liver and turns abruptly to the left

the colon continues across the abdomen to the left side. It curves beneath the inferior end of the spleen on the left side and passes inferiorly to the level of the iliac crest as the descending colon

begins near the left iliac crest, projects medially to the midline, and terminates as the rectum at about the level of the third sacral vertebra

lies anterior to the sacrum and coccyx

the terminal 2-3 cm of the rectum

the mucous membrane of the anal canal are arranged into these longitudinal folds that contain a network of arteries and veins

the opening of the anal canal to the exterior is guarded by an internal anal sphincter of smooth muscle tissue and an external anal sphincter of skeletal muscle( voluntary)

portions of the longitudinal smooth muscle in the muscularis are thickened forming three conspicuous bands that run most of the length of the large intestine.

tonic contractions of the teniae coli gather the colon into a series of pouches which give the colon a puckered appearance

immediately after a meal this reflex intensifies peristalis in the ileum and forces andy chyme into the cecum

a movement characteristic of the large intestine.  In this process the haustra remain relaxed and become distended while they fill up.  when distension reaches a certain point the walls contract and squeeze the contents into the next haustrum

a strong perstalltic wave that begins at about the middle of the transverse colon and quickly drives the contents of the colon into the rectum

initiated by food in the stomach, this reflex in the colon causes mass peristalis usually 3-4 times a day during or immediately after meals

consists of water, inorganic salts, epithelial cells, bacteria and undigested food.

mass peristaltic movement pushes feces from  the sigmoid colon into the rectum.  The resulting distension of the rectal wall stimulates stretch receptors which initiates this reflex that empties the rectum

is an increase in the frequency, volume, and fluid content of the feces caused by increased motility of and decreased absorption by the intestines

refers to the infrequent or difficult defecation caused by decreased motility of the intestines