The rectum is the name given to the lowest part of the bowel - or the gastrointestinal tract.
The rectum is found in the pelvis. It is 15 cm long and curves side to side with three curves. It is used as a storage for faeces and gas and so it is able to distend to quite a large size before having to empty.
This ability to distend is a property not only of the wall but also the curves. As the rectum is not under any stretch or tension, it distends quite significantly without a problem. This means that you are able to go quite a long periods before needing to open your bowels.
Above the rectum is the sigmoid colon which is the last part of the large bowel before the rectum. The junction between sigmoid colon and rectum is at the level of the pelvis - so the sigmoid colon is in the abdomen and the rectum is in the pelvis.
At the other end of the rectum, is the anal canal. The junction between the rectum and the anus is a very specialised area. Sensors in this area allow you to tell, without thinking, whether there is gas or faeces trying to leave the rectum. It is this that allows humans to pass wind without soiling themselves.
There are several conditions that affect the rectum including polyps, cancer and inflammatory bowel disease such as Crohns or ulcerative colitis.
As the rectum is in the pelvis, surgery to the rectum and investigations can be quite difficult. Specialists in this area can come from a medical or surgical background. Colo-proctologists or colorectal surgeons, surgeons that specialise in conditions of the colon, rectum and anus.