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The colon lies within the abdomen. It is part of the digestive system, and specifically part of the large intestines. The anatomy of the colon starts after the cecum and ends before the rectum. It is a hollow muscular tube which carries out a number of digestive functions.
Overall, colon anatomy has four main sections. The section known as the ascending colon starts at the cecum and extends upward on the right side of the abdomen to just underneath the liver. At this point, it turns sharply to the left. The area of the turn is called the hepatic flexure. After the hepatic flexure, the section of the colon is called the transverse colon.
The transverse colon is the longest section of the large intestines. This colon anatomy section is very mobile, and it extends across the abdomen and underneath the stomach, from right to left. The transverse colon turns downward at the spleen at what is called the splenic flexure. After the turn, the transverse colon changes into the descending colon.
Traveling down the left side of the abdomen, the descending colon curves in an “S” shape at its end. The area of the curve is known as the sigmoid colon. This final section in the anatomy of the colon ends in the anal canal, or rectum.
Structurally, the anatomy of the colon is made up of serous, muscular, and mucous membrane layers of tissues. The colons muscle fibers are longitudinal. These fibers form three bands called teniae coli, which create pouches known as haustra.
Colon physiology plays an important role in digestion. The colon secretes mucus, and this mucus provides protection from potentially abrasive materials as they pass through the large intestines. Mucus helps moderate the pH balance in the colon and causes fecal material to adhere to other fecal material.
Other colon functions include absorbing water and electrolytes from the food that is digested. This preserves water and reduces the amount of fluid needed, preventing dehydration. Along with preserving water and electrolytes, the colon aids in obtaining nutrition from the food that passes through.
Intestinal flora are hosted in the colon. The flora are distinct from human digestive enzymes, and they can decompose cellulose that human digestive enzymes cannot. Vitamins are manufactured by the intestinal flora. These vitamins are riboflavin, thiamine, B12, and K.
The anatomy of the colon enables it to store, mix, and move the materials that pass through it. Bowel movements usually occur two or three times daily, unless the colon or other parts of the large intestines are irritated. An example of this irritation is the condition known as colitis.