The rectum is the final straight portion of the large intestine that begins at the end of the sigmoid colon and ends at the anus. It is where stool is held before it passes out of the body through the anus. The rectum is about 6 inches long and has a slight "S" shape with two bends in it that help control continence. The rectum absorbs excess water from stool and holds it until its full, when nerves trigger the urge to defecate. The rectum is made up of layers of muscles and tissues, with glands on the inside that secrete and absorb. The rectum acts as a temporary storage site for feces, and as the rectal walls expand due to the materials filling it from within, stretch receptors from the nervous system located in the rectal walls stimulate the desire to pass feces, a process called defecation.