The ascending colon, one of the many parts of the large intestine, is located on the right side of the body. It begins at the cecum and ends at the hepatic flexure, where the colon turns to the left from the transverse colon. The function of the ascending colon is to reabsorb water, vitamin K, and potassium present in the fecal matter. This part of the large intestine also continues the bacterial breakdown of fecal matter begun in the small intestine and to move the fecal matter toward the rectum for excretion.
Located on the right side of the abdomen, the ascending portion of the colon is an extension of the small intestine. There are four parts to the colon, the ascending, transverse, descending, and sigmoid colon. The ascending section of the colon is usually between 5 and 8 inches (13 and 20 cm) in length and is about 1 inch (2.5 cm) thick.
The ascending portion of the colon is home to hundreds of different species of bacteria. The job of these microbes is to further break down the fecal matter passed from the small intestines. As the waste is metabolized by the bacteria, some vitamins, especially vitamin K, is released into the open space of the colon and is made available for absorption by the body. The vitamin K made available by the bacteria in the ascending colon does not supply all of the vitamin K needed by the body, but it is an important part of body’s need for this essential nutrient.
The surface of the ascending colon is covered with a membrane that is embedded with aquaporins, or specialized openings in the lining of the colon. Water and electrolytes, such as vitamin K and potassium, are driven via an osmotic gradient out of the ascending colon. This means that water and electrolytes, at a high concentration inside the colon, are driven to an area of low concentration of water and electrolytes outside the colon. Allowing the movement of these substances are the aquaporins.
When fecal matter enters the ascending portion of the colon, it is fairly watery. As water is reabsorbed from the fecal matter, it becomes much denser and compacted. It changes from a soupy substance to a dough-like matter. The walls of the ascending section of the colon are lined with muscles that contract and expand to force the fecal matter along through the rest of the colon and eventually to the rectum for excretion. Muscular contractions in the ascending colon also act to concentrate and consolidate the fecal matter to make excretion easier.