Rectum – the rectum is the very last section of the colon; at the top it joins the sigmoid colon, and at the bottom it ends at the anus via the anal canal.
The rectumlies in the pelvic cavity, in front of the sacrum and the coccyx. The rectumis approximately 12 centimetres long. Stool is stored here before it is passed; as it fills, this section of bowel widens into a jug shape.
The rectum is lined with a reddish, shiny mucous membrane containing glands, and the connective tissue beneath it contains a winding network of veins.
The rectumhas two ring-shaped sphincter muscles in its wall, whose job is to control bowel movements. The internal sphincter is under involuntary control, while the external sphincter lies directly at the outlet of the rectum, that is, at the anus, and is under voluntary control.
The rectumand the coordinated movement of the two sphincters together allow stool to leave the intestinal tract.
