Colon And Rectum

Colon And Rectum

The material left behind after nutrients are absorbed passes from the small intestine to the large, or colon, intestine, a U-shaped tube with a larger diameter and thicker walls than the small intestine. The colon consists of three parts: ascending, transverse and descending.

The small intestine flows into the large intestine from the side, at some distance from its end, forming a large sac, the so-called cecum, ending in a small appendage the size of a little finger - the appendix, or vermiform appendix. From the junction of the small and large intestines, the ascending colon runs up the right side of the body to the level of the liver, then turns at a right angle and, having passed into the transverse colon, crosses the abdominal cavity directly under the liver and stomach.

Having reached the left side of the body, it makes another straight turn and, in the form of a descending colon, passes along the left side of the body down to the rectum.

The material that passes from the small intestine to the large intestine has already been deprived of most of the nutrients as a result of absorption, but it still has a liquid consistency. The main function of the colon is to absorb water and convert the contents into a semi-solid state.

Defecation occurs partly voluntarily, due to muscle contraction and relaxation of the anal sphincter, partly involuntarily due to relaxation of the internal sphincter and contraction of the colon and rectum.

It takes 12-24 hours for undigested residues to pass through the colon and rectum. The final product (stool) contains food debris, substances excreted by the body, and large amounts of bacteria.