The rectum is the final straight section of the large intestine, a muscular tube about 12 to 15 centimeters (roughly 5 to 6 inches) long that connects your colon to your anus. Its primary job is holding stool until you’re ready to have a bowel movement. Though it’s a short segment of the digestive tract, the rectum plays a surprisingly active role in how your body senses, stores, and eliminates waste.
Where the Rectum Sits in Your Body
The rectum begins deep in the pelvis at the level of the third sacral vertebra, which is in the lower part of your spine just above the tailbone. It’s a direct continuation of the sigmoid colon, the S-shaped section of the large intestine that feeds into it. From there, it descends along the curve of the sacrum and ends where it meets the anal canal, at a muscular floor called the levator ani. That muscular boundary marks the transition from rectum to anus.
Unlike most of the colon, which winds and loops through your abdomen, the rectum follows a relatively straight path. The word itself comes from the Latin for “straight intestine.” It sits behind the bladder in men and behind the uterus and vagina in women, which is why a doctor can sometimes feel nearby organs during a rectal exam.
How the Rectal Wall Is Built
The rectal wall has four distinct layers, each with a specific role. The innermost layer, the mucosa, lines the interior and produces mucus that helps stool pass smoothly. Beneath that sits the submucosa, a layer packed with connective tissue, nerve fibers, and small blood vessels. The third layer, the muscularis, contains two sheets of smooth muscle: an inner ring that encircles the tube and an outer layer that runs lengthwise. These muscle layers work together to push stool downward. The outermost covering is a thin tissue layer that separates the rectum from surrounding structures in the pelvis.
This layered design matters because it determines how diseases like cancer are staged. A growth confined to the mucosa, for example, is far less serious than one that has pushed through the muscle layers into surrounding tissue.
Storage, Sensing, and the Urge to Go
The rectum does two things with incoming stool depending on volume. When a small amount of fecal material arrives from the sigmoid colon, the rectal muscles stretch gently and accommodate it, storing the waste until more accumulates. This adaptability is what allows you to go hours between bowel movements rather than needing to empty your bowels every time material enters the rectum.
Once enough stool builds up, the stretching triggers pressure-sensitive receptors embedded in the rectal wall. These receptors fire signals to your brain that register as the familiar urge to have a bowel movement. At the same time, a reflex causes the internal anal sphincter, a ring of muscle at the top of the anal canal, to relax automatically. This sphincter operates entirely outside your conscious control.
The external anal sphincter, located just below it, is the one you do control. It stays contracted until you decide the time and place are right, then relaxes to allow stool to pass. The coordination between these two sphincters is what gives you continence. If either one is damaged through injury, surgery, or nerve problems, the result can be difficulty holding stool or incomplete emptying.
Blood Supply to the Rectum
The rectum receives most of its blood from the superior rectal artery, a branch of the artery that supplies the entire left side of the colon. Two additional vessels, the middle and inferior rectal arteries, provide backup flow. These arteries connect with each other through a rich network, which means the rectum generally maintains good blood supply even if one vessel is compromised. This network of veins near the lower rectum and anus is also where hemorrhoids develop when the vessels become swollen.
Common Conditions That Affect the Rectum
Because the rectum is the last stop before waste leaves the body, it’s vulnerable to a range of conditions. Some are minor nuisances, others require close medical attention.
Hemorrhoids are swollen blood vessels in or around the rectum and anus. They’re extremely common, often triggered by straining during bowel movements, pregnancy, or prolonged sitting. Symptoms include itching, discomfort, and bright red blood on toilet paper or in the bowl.
Proctitis is inflammation of the rectal lining. It can result from inflammatory bowel disease, radiation therapy to the pelvic area, or sexually transmitted infections. Symptoms typically include rectal bleeding, mucus or pus discharge, pain during bowel movements, and a persistent feeling of needing to go even when the rectum is empty (a sensation called tenesmus). Some forms come and go in cycles of flare-ups and remission.
Rectal prolapse occurs when part of the rectal wall slides downward and protrudes through the anus. It’s more common in older adults and in people with a history of chronic straining or weakened pelvic floor muscles.
Anal fissures and fistulas are tears or abnormal tunnels that can form in or near the rectal and anal tissue, often as complications of chronic inflammation, Crohn’s disease, or infection. They tend to cause sharp pain during bowel movements and sometimes drainage.
Rectal Cancer and Screening
Rectal cancer develops when cells in the rectal lining grow abnormally and form tumors. It shares many features with colon cancer, and the two are often grouped together as colorectal cancer, one of the most common cancers worldwide. Early-stage rectal cancer frequently produces no symptoms at all, which is why routine screening matters.
The U.S. Preventive Services Task Force recommends that all adults at average risk begin colorectal cancer screening at age 45 and continue through age 75. This threshold was lowered from 50 in recent years after data showed rising rates of colorectal cancer in younger adults. Several screening methods exist, ranging from stool-based tests you do at home to colonoscopy, which allows a doctor to visually inspect the entire rectum and colon and remove precancerous growths called polyps on the spot.
People with a family history of colorectal cancer, inflammatory bowel disease, or known genetic conditions like Lynch syndrome often need to start screening earlier and may need it more frequently.
Signs of a Rectal Problem
Any persistent change in how your bowels work deserves attention. Rectal bleeding is the symptom that sends most people searching for answers, and while hemorrhoids are the most common cause, bleeding can also signal inflammation, polyps, or cancer. Other symptoms worth noting include a new or worsening feeling of incomplete emptying, unexplained changes in stool shape (particularly pencil-thin stools), persistent rectal pain, or mucus discharge. These don’t automatically mean something serious, but they’re the body’s way of flagging that something in the rectum isn’t functioning normally.