What is the colon?

The colon is the longest part of the large bowel or large intestine, measuring around 60 inch (1.5 m). The large bowel is a tube-like organ that begins from the small intestine and ends at the anus. The colon extends from a pouch-like structure called the cecum and ends at the rectum (the part of the large bowel where stools are stored). The rectum is the lowest part of the large bowel and measures around 8 inch in length.
Structurally, the colon is divided into four main parts:
- Ascending colon: This is the first part of the colon. It begins from the cecum, which acts as the connecting link between the colon and the last part of the small bowel (ileum). When it meets the right lobe of the liver, it turns 90 degrees to move horizontally. This turn is known as the right colic flexure (or hepatic flexure) and marks the start of the transverse colon.
- Transverse colon: It begins at the right colic flexure (the site where the ascending colon takes a sharp 90-degree turn) and moves horizontally (transversely). At the level of the spleen, the transverse colon takes a 90-degree turn and continues as the descending colon.
- Descending colon: It begins at the left colic flexure (the site where the transverse colon takes a 90-degree turn) and moves downward (descends) toward the pelvis.
- Sigmoid colon: It is an ‘S’ shaped structure measuring around 15.7 inch. It is the last part of the colon and begins when the descending colon moves toward the midline (medially). It is the narrowest part of the colon.
What does your colon do?
The colon is a crucial part of the digestive system that starts from the mouth and ends at the anus. Digestion of food begins in the mouth. The swallowed food passes into the food pipe (esophagus) and continues its journey through the gut, moving from the stomach, small intestine, and large intestine and finally being expelled from the anus. Each part of the gut serves important functions in digesting the food and absorbing essential nutrients and water. The digestive tract also helps remove harmful and useless substances from the body. By the time the food enters the colon, most of the digestion has been done. The major functions of the colon include:
- Absorption of water, electrolytes (minerals), and some other nutrients from the digested food.
- The bacteria present in the colon help digest some of the partially digested food and may help make important substances, such as vitamin K.
- The colon bacteria also help in preventing the growth of harmful bacteria and help maintain gut health.
- The regular muscular contractions of the colon (the peristaltic waves) help move the digested food toward the rectum from where it can be expelled through the anus.
- The lymphoid tissue and bacteria present in the colon help maintain immunity and keep the person healthy.

QUESTION
What percentage of the human body is water? See AnswerHow can I keep my colon healthy?
Gut health is essential for maintaining overall health. The colon can be affected by several health conditions, such as Crohn’s disease, ulcerative colitis, diverticulitis, colon polyps, and colon cancer. As many of these conditions may occur in the absence of any obvious cause, the colon can be kept healthy through certain habits, which include:
- Eating a high fiber diet rich in fruits and vegetables
- Maintaining a healthy weight
- Avoiding alcohol and tobacco consumption
- Drinking plenty of water
- Avoiding fatty, sugary, deep-fried, and grilled foods
- Avoiding sugary beverages
- Exercising regularly
- Avoiding unnecessary antibiotics
- Having probiotics, such as yogurts, kefir, may help maintain gut health as well
If there is some problem with the colon, there could be symptoms, such as abdominal pain, bloating, diarrhea, constipation, fever, bleeding through the rectum, nausea, vomiting, or unexplained weight loss. Consult a doctor right away if any of these symptoms appear for timely diagnosis and treatment.
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Medline Plus. Colonic Diseases. https://medlineplus.gov/colonicdiseases.html
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