The colon, also known as the large intestine, is an important portion of the human digestive system. The colon is located between the small intestine and rectum in the digestive tract and is a hollow tube that is approximately 5 feet long and 2 to 3 inches wide. The colon has vital functions in the digestive process but it is also subject to a variety of diseases, some which can be extremely serious.
The colon has the appearance of an upside-down letter "U" and is composed of four major sections. It lies within the abdominal cavity, starting in the lower right-hand portion of this region in the area of the waist. The ascending colon is located near the liver and begins at the cecum before it goes upwards where it meets the transverse colon, the section that stretches across the body and is supported by a band of tissue. From the transverse colon the colon goes downwards; this is called the descending colon. It turns into the sigmoid colon which connects to the rectum.
The function of the human colon is to bring waste materials from the small intestine all the way to the rectum for expulsion from the body. When food has passed through the small intestine all of the valuable nutrients in it have already been removed. The colon will absorb the little water that is left in this waste along with such minerals as sodium. Once this has occurred the waste is known as stool and is stored in the colon until a person has a bowel movement.
Maintaining the fluid balance of the body is a key job of the colon. It will absorb vitamins through its walls and then process the waste material into feces. It does this by mixing the indigestible parts of the ingested food known as fiber with water, mucus, vitamins, and the bacteria that inhabit the colon to form feces. While the feces moves along through the colon the bacteria that live in the colon will feed on the fiber within it and provide nutrients for the cells lining the intestine. When the walls of the sigmoid colon contract the waste products are moved to the rectum. This contraction is called peristaltic action and is a motion not unlike a wave that helps the feces along the tract and finally out of the anus.
A common problem many people encounter is constipation, which involves the colon. In this condition hard feces develop within the colon that become difficult to get rid of. This occurs most often when the colon absorbs more water than it should from the waste products moving through it. The feces become hardened and dried out. Expelling them can be painful and in severe cases the colon can become blocked and obstructed. There are a variety of reasons for constipation, from poor diet to medication side effects to a number of illnesses.
The colon is vulnerable to an assortment of diseases, some of which are very serious. Colitis and Crohn's disease are inflammatory ailments that affect the colon and cause discomfort among other symptoms. Irritable bowel syndrome can be very painful in some instances and result in bloating and constipation. Diverticulitis involves small pouches that develop on the outside of the colon that become infected or swollen. Colon cancer is the third most frequently seen form of cancer and a potentially fatal type that develops from polyps located in the colon.