From the small intestine, food that has not been digested (mostly fiber and water) travels into your large intestine (colon) through a muscular ring that prevents food from returning to the small intestine. The main function of the large intestine is to remove water from the undigested matter and form solid waste that can be excreted as stool (feces) during a bowel movement.
The first part of the colon is called the cecum, a pouch that joins the small intestine to the large intestine. A small, hollow, finger-like pouch, called the appendix hangs from the end of the cecum. It no longer appears to be useful to the digestive process.
The appendix has no known function and is not involved in the digestive process. Normally, the appendix is open to the intestine, but it can become blocked by hardened stool, swollen tissue, or parasites. It also can become inflamed, causing a condition known as appendicitis.
The colon extends from the cecum up the right side of the abdomen (the ascending colon), across the upper abdomen (the transverse colon), and then down the left side of the abdomen (the descending colon), finally connecting with the rectum.
Helpful bacteria in the colon help to digest the remaining food products, as the walls of your colon absorbs nearly all of the remaining water, leaving a soft, formed substance called stool (feces).
Muscles in the wall of your colon separate the waste into small segments of stool that are pushed into your lower colon and rectum. The accumulation of stools stretches the walls of your rectum and signals the need for a bowel movement.
When you relax the sphincter muscle in your anus, the muscles in the wall of your rectum contract and the increase in pressure pushes out the stool. If the stool is very firm you may have to use your abdominal muscles, which press on the outside of the colon and rectum.
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