Rectum

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Rectum
Anorectum.gif
Anatomy of the anus and rectum
Gray1077.png
Posterior aspect of rectum exposed by removing lower part of sacrum and coccyx
Gray'ssubject #249 1183
Arterysuperior rectal artery (first two-thirds of rectum), middle rectal artery (last third of rectum)
Veinsuperior rectal veins, middle rectal veins
Nerveinferior anal nerves, inferior mesenteric ganglia[1]
Lymphinferior mesenteric lymph nodes, pararectal lymph nodes, internal iliac lymph nodes, Deep inguinal lymph nodes
PrecursorHindgut
MeSHRectum
 
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"Rectal" redirects here. For the route of administration, see Rectal (medicine).
For the conic sections see Latus rectum or Semi-latus rectum
Rectum
Anorectum.gif
Anatomy of the anus and rectum
Gray1077.png
Posterior aspect of rectum exposed by removing lower part of sacrum and coccyx
Gray'ssubject #249 1183
Arterysuperior rectal artery (first two-thirds of rectum), middle rectal artery (last third of rectum)
Veinsuperior rectal veins, middle rectal veins
Nerveinferior anal nerves, inferior mesenteric ganglia[1]
Lymphinferior mesenteric lymph nodes, pararectal lymph nodes, internal iliac lymph nodes, Deep inguinal lymph nodes
PrecursorHindgut
MeSHRectum

The rectum (from the Latin rectum intestinum, meaning straight intestine) is the final straight portion of the large intestine in some mammals, and the gut in others. The human rectum is about 12 centimetres (4.7 in) long, [2] and begins at the rectosigmoid junction (the end of the sigmoid colon), at the level of the third sacral vertebra or the sacral promontory depending upon what definition is used. [3] Its caliber is similar to that of the sigmoid colon at its commencement, but it is dilated near its termination, forming the rectal ampulla. It terminates at the level of the anorectal ring (the level of the puborectalis sling) or the dentate line, again depending upon which definition is used. [3] In humans, the rectum is followed by the anal canal, before the gut terminates at the anal verge.

Contents

Role in human defecation

The rectum intestinum acts as a temporary storage site 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 from the feces. If defecation is delayed for a prolonged period, constipation and hardened feces results.[citation needed]

When the rectum becomes 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.

Supports of rectum

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.

The endoscopic procedures colonoscopy and sigmoidoscopy are performed to diagnose diseases such as cancer.

Digital Rectal Stimulation, the insertion of one finger into the rectum, is used to induce peristalsis in patients whose own peristaltic reflex is inadequate to fully empty the rectum.

Manual Evacuation is the use of a gloved finger to evacuate faeces from the rectum, and is utilised primarily in acute constipation and also the long-term management of neurogenic bowel, seen most frequently in people with a spinal cord injury or multiple sclerosis.

Rectum

Temperature taking

related article: rectal thermometry

Body temperature can also be taken in the rectum. Rectal temperature can be taken by inserting a medical thermometer not more than 25 mm (1 inch) into the rectum via the anus. A mercury thermometer should be inserted for 3 to 5 minutes; a digital thermometer should remain inserted until it beeps. Normal rectal temperature generally ranges from 36 to 38 °C (97.6 to 100.4 °F) and is about 0.5 °C (1 °F) above oral (mouth) temperature and about 1 °C (2 °F) above axilla (armpit) temperature.[citation needed]

Pediatricians recommend that parents take infants' and toddlers' temperature in the rectum for two reasons:

  1. Rectal temperature is the closest to core body temperature and in young children, accuracy is critical.
  2. Younger children frequently do not cooperate when having their temperature taken by mouth (oral), which is recommended for children ages 6 and above as well as adults.

In recent years, the introduction of tympanic (ear) thermometers and changing attitudes on privacy and modesty have led some parents and doctors to discontinue taking rectal temperatures.[citation needed]

Sexual stimulation

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 or penetration can result in sexual arousal. For further information on this aspect, see anal sex.

Additional images

Median sagittal section of male pelvis, showing arrangement of fasciæ  
Arteries of the pelvis  
Median sagittal section of male pelvis  
Median sagittal section of female pelvis  
Sagittal section of the lower part of a female trunk, right segment  
Blood vessels of the rectum and anus
Blood vessels of the rectum and anus  
Organs of the female reproductive system
Cross-section microscopic shot of the rectal wall  
Section of mucous membrane of human rectum (60×)  
Dog Rectum cross-section (40×)  
Dog Rectum cross-section (400×)  
Rectum  

See also

References

  1. ^ Physiology at MCG 6/6ch2/s6ch2_30
  2. ^ "12. Colon and Rectum", AJCC Cancer Staging Atlas, American Joint Committee on Cancer, 2006, p. 109, http://www.springer.com/cda/content/document/cda_downloaddocument/colon_rectum_chpt_14.pdf?SGWID=0-0-45-313390-0 
  3. ^ a b al.], senior editors, Bruce G. Wolff ... [et (2007). The ASCRS textbook of colon and rectal surgery. New York: Springer. ISBN 0-387-24846-3. 

External links