The colon forms the biggest section of the large intestine, which is the tube through which digested food passes. Digestive system juices join that food, which includes gastric acid along with bile, on its course through the digestive tract. This partially fluid mass, called chyme, is not all just waste material and a lot of things happen to it before it leaves the body.
The partially digested material that leaves the small intestine still contains a substantial amount of water, fluid that the body retains naturally. The muscular and chemical action within the colon helps to remove that water from the chyme along its journey, a trip through the roughly five feet of colon within the abdominal cavity. However, extracting that water is not only a question of efficiency.
Proper water balance is crucial to a large number of the chemical reactions within the body, in addition to playing an important part in internal temperature regulation. The colon does considerably more than simply pack digested food into feces for elimination. While that water is being removed several other important processes are also happening. There are more than seven hundred types of bacteria living in the 'gut', a good number of them playing a vital role in digestion as well as health. Amongst other things, they help produce vitamins K and Biotin (a member of the B-complex family of vitamins).
What is the Colon Function
The colon assimilates several of the products of the digestive processes of the bacteria themselves, then passes them back into the blood stream. The blood then distributes those nutrients to tissues all over the body. This is just one reason that anti-biotics should be taken with care. They not only suppress harmful bacteria but the beneficial ones, as well.
Those bacteria are also responsible for producing the gas, known as flatus, which occasionally upsets your stomach or fouls the air. As they consume undigested polysaccharides usually in the form of human indigestible fiber that we eat, they produce that gas. The gas by itself is not, contrary to popular thinking, mostly methane or hydrogen sulphide (egg gas). It is predominantly nitrogen and carbon dioxide, with trace levels of those other molecules, together with a small amount of hydrogen.
Once those bacteria break down fiber they are producing nutrients not just for their own survival, but also the vitamins mentioned above. At the same time, they produce compounds that offer nourishment for the cells that line the colon (the epithelium). In addition they contribute to creating lymphatic cells which form a key element of the body's immune system.
The chyme, now completely processed, will continue to move along the colon by a slow process of muscular contraction called peristalsis. The python like contracting and relaxing moves the material ultimately down into the rectum, compacting it and removing water to form feces. The actual rectum is the six inch or so tube just up from the rectum, the opening. The feces are then squeezed out of the rectum in a bowel motion.
The entire process usually takes ten to twelve hours and, as you can tell, entails a lot more than merely pushing digested food waste through a two and a half inch diameter tube. It is a necessary partner in whole body health.