This last portion of the human gastrointestinal tract is approximately 5 to 5.5 feet long with a diameter of about 2.5 inches.
The colon is basically concerned with the removal of solid wastes (stool) generated in the digestion of food, reabsorption of water from the waste products, and the absorption of electrolytes and certain vitamins. It is also the site, where the intestinal flora, especially the friendly bacteria reside and carry out the fermentation of the undigested food.
The Structure and Location
The human and mammalian colon can be divided into four sections : ascending, transverse, descending, and sigmoid colon. The colon is actually portion of the large intestine that is located between the caecum and the rectum. The caecum is the first portion of the large intestine, which connects the colon to the last part of the small intestine, i.e., ileum.
The colon begins on the lower right side of the abdominal cavity, where the caecum ends. From this point, it ascends to the level of the liver or the hepatic flexure. This is the first part of the colon, i.e., the ascending colon, which is approximately 25 cm long.
At the hepatic flexure, the colon takes a sharp turn to the left and crosses the abdominal cavity. This portion is called the transverse colon. At the level of the spleen, or the splenic flexure, it moves down to the left.
This portion is known as the descending colon. The last part of the colon is sigmoid colon, which is the S-shaped portion that comes after the descending colon and before the rectum.
What is the Function of the Colon?
As mentioned already, the colon works as the storage organ for the solid waste products or stool. It is also responsible for reabsorbing water from solid wastes, and thus maintain water balance in the body.
Apart from these, it serves at the site where beneficial bacteria and other microorganisms thrive and help ferment undigested and unabsorbed food material, and synthesize some vital nutrients like folic acid.
The beneficial bacteria also check the growth of harmful bacteria, and maintain the pH of the body. Vital electrolytes and some vitamins, especially vitamin B and vitamin K are absorbed in this part of the large intestine.
However, the most crucial function of this organ is the elimination of waste material in the form of stool or feces through the rectum. The muscles of the intestine contract in a wave-like manner to pass the stool down to the rectum.
Generally, the stool is liquid when it enters the first part of the colon. As this liquid waste material moves through the colon, all excess water is absorbed from it so that by the time it reaches the descending colon, it becomes semi-solid.
In the descending part of the colon, the waste material is stored, until it is emptied into the rectum. Defecation takes place, when the muscles of the sigmoid colon contract to increase the pressure inside the colon, so that the stool can move and enter the rectum. The bulkier the stool is, the more easily it can be moved and expelled by the colon.
The stool becomes bulkier, when it contains more fiber. This is the reason why fiber-rich foods should be included in the diet to ensure regular bowel movements. Usually, an individual can have two to three bowel movements in a day, if the colon is healthy and functioning properly.
The bacteria present in the colon break down the fiber for their nourishment, and in the process generate acetate, propionate, and butyrate as by products, which nourish the cells lining the colon.
When the normal functions of this organ are disrupted, one can experience several health problems, mainly due to the accumulation of the toxic waste material, and the impaired absorption of some vital nutrients. The colon can fail to function properly, when we do not follow a healthy lifestyle and diet.
So, a balanced diet with lots of fruits and other fiber-rich foods can prove immensely beneficial for the health of the colon.