Colon – the colon is the last section of the digestive tract, about 1.5 metres long. It lies in the abdominal cavity in the shape of a question mark.
The coloncan be divided into several parts. At the bottom of the caecum is the opening of the appendix. At the junction of the caecum and the ascending (right) colonthe small intestine opens into it through a valve. The section between the colonliverand spleen flexures is the transverse colon, followed by the descending (left) colonand the rectum-adjoining, S-shaped sigmoid colon.
The appendix, a tube shaped like a little finger that functions as an important lymphatic organ, arises from the caecum. The colonsecretes mucus and plays an important role in absorbing water from the colon's contents.
Its task is to concentrate the non-absorbable material that reaches it (containing digestive juices that are no longer needed, indigestible food residues, cells shed from the intestinal lining, dead bacteria, and small amounts of proteins and fats), and to eliminate waste.
On an average diet, about 75-170 g of stool is passed per day. The colonhas a rich bacterial flora that can break down cellulose, produce vitamin K and putrefy protein in an alkaline environment.
The colon's countless bacteria digest certain substances further, producing gas in the process. Bacteria are needed for healthy bowel function, but certain diseases and antibiotics can upset the balance of the different bacteria in the colon. This imbalance (dysbacteriosis) can cause mucus and water secretion and diarrhoea.
