The rectosigmoid colon is an often overlooked part of the digestive system. It is located near the end of the large intestine and serves to join the distal, or most distant, part of the sigmoid colon to the rectum. It is at this point in the digestive system that the large intestine, or colon, transitions into the rectum. It comprises only a small portion of the large intestine, but the rectosigmoid serves an important function as a connection point between the sigmoid colon and the rectum. Without the healthy functioning of the rectosigmoid, many health complications, including constipation, could develop.
The sigmoid colon, the portion of the colon situated above the rectosigmoid, also is referred to as the pelvic colon. It is located on the lower left area of the abdomen. This part of the colon measures approximately 16 inches (40 cm) in length and is responsible for creating strong contractions that are aimed at creating and maintaining high pressure in the colon. It is this action that is utilized by the body to regulate the movement of stool into the rectum.
The formation of diverticuli is common because of the high pressure in the sigmoid colon. Diverticuli are pockets or projections that sometimes form in the colon, and they can lead to such symptoms as pain or discomfort, nausea, constipation or even diarrhea. The presence of these diverticuli is known as diverticulosis. Increasing fiber intake is often a good choice for this condition, and other dietary changes sometimes are necessary as well. In rare cases, surgery becomes necessary, so proper medical care is essential when there are any intestinal concerns present.
As the rectosigmoid part of the colon leaves the sigmoid portion of the colon, it leads into the rectum, which is located at the end of the intestinal tract. It measures approximately 5 inches (12 cm) in length and serves as a temporary storage spot for feces before it leaves the body. Pressure inside the rectum causes the rectum to shorten as feces is emptied from the body through the anus. Both internal and external sphincter muscles are part of the anal canal. These muscles are used to stretch the anus over the fecal material leaving the intestines so that it can be removed from the body.
The complete function of the rectosigmoid portion of the colon itself is not fully understood in the medical community. At the very least, however, it serves to connect very important portions of the large intestine. As such, it is a vital part of human anatomy.