The Rectum is the final portion of the large intestine in some mammals, and the gut in others, terminating in the anus.

Medical procedures

For the diagnosis of certain ailments, a rectal exam may be done. Suppositories may be inserted into the rectum as a route of administration for medicine.

Electroejaculation may be conducted for the treatment of anejaculation and ejaculatory dysfunction in men.

Body temperature can also be taken in the rectum. Rectal temperature can be taken by inserting a mercury thermometer for 2-3 minutes, or a digital thermometer until it "beeps", not more than an inch into the rectum via the anus. Due to recent concerns related to mercury poisoning, the use of mercury thermometers is now discouraged. Normal rectal temperature generally ranges from 97.6 degrees Fahrenheit to 100.4 degrees Fahrenheit and is roughly one degree above oral (mouth) temperature and roughly two degrees above axillary (armpit) temperature. On average, the rectal temperature is 0.7 degrees higher than oral temperature. Many pediatricians recommend that parents take infants and toddler's temperature in the rectum for two reasons: (1) Rectal temperature is the closest to core body temperature and in children that young, accuracy is critical. (2)Younger children are unable to cooperate when having their temperature taken by mouth (oral) which is recommended for children, ages 6 and above and for adults. In recent years, the introduction of ear (tympanic) thermometers and changing attitudes on privacy and modesty have led some parents and doctors to discontinue taking rectal temperatures.

The rectum in human defecation

The rectum ampulla acts as a temporary storage facility for feces. 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 defecate. If the urge is not acted upon, the material in the rectum is often returned to the colon where more water is absorbed. If defecation is delayed for a prolonged period constipation and hardened feces results.

When the rectum is full the increase in intrarectal pressure forces the walls of the anal canal apart allowing the fecal matter to enter the canal. The rectum shortens as material is forced into the anal canal and peristaltic waves propel the feces out of the rectum. The internal and external sphincter allow the feces to be passed by muscles pulling the anus up over the exiting feces.

See defecation for a fuller treatment.

Muscular anatomy of the human pelvis and rectum

The Levatores ani constrict the lower end of the rectum and vagina. They elevate and invert the lower end of the rectum after it has been protruded and everted during the expulsion of the feces. They are also muscles of forced expiration. The Coccygei pull forward and support the coccyx, after it has been pressed backward during defecation or parturition. The Levatores ani and Coccygei together form a muscular diaphragm which supports the pelvic viscera.

Sexual stimuli

Due to the proximity of the anterior wall of the rectum to the vagina in females or to the prostate in males and the shared nerves thereof, rectal stimulation can result in sexual arousal. As a human sexual behavior, often this takes the form of anal intercourse or penetration with specialised anal sex toys such as butt plugs.