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Anatomy of the anus and rectum

Defecation is the final act of digestion, by which organisms eliminate solid, semisolid, and/or liquid waste material from the digestive tract via the anus.

Humans expel feces with a frequency varying from a few times daily to a few times weekly.[1] Waves of muscular contraction (known as peristalsis) in the walls of the colon move fecal matter through the digestive tract towards the rectum. Undigested food may also be expelled this way, in a process called egestion.

Open defecation is the practice of defecating outside or in public, i.e. without using a toilet of any kind, mostly due to extreme poverty in developing countries.



The rectum ampulla (anatomically also: ampulla recti) temporarily stores fecal waste. As the waste fills the rectum and expands the rectal walls, nervous system stretch receptors in the rectal walls stimulate the desire to defecate. This urge to defecate arises from the reflex contraction of rectal muscles, relaxation of the internal anal sphincter, and an initial contraction of the skeletal muscle of the external anal sphincter. If the urge is not acted upon, the material in the rectum is often returned to the colon by reverse peristalsis, where more water is absorbed and the faeces is stored until the next mass peristaltic movement of the transverse and descending colon. If defecation is delayed for a prolonged period the fecal matter may harden, resulting in constipation. If defecation occurs too fast, before excess liquid is absorbed, diarrhea may occur.[2]

When the rectum is full, an increase in intra-rectal pressure forces apart the walls of the anal canal, allowing the fecal matter to enter the canal. The rectum shortens as material is forced into the anal canal and peristaltic waves push the feces out of the rectum. The internal and external anal sphincters along with the puborectalis muscle allow the feces to be passed by muscles pulling the anus up over the exiting feces.[citation needed]

Defecation is normally assisted by taking a deep breath and trying to expel this air against a closed glottis (Valsalva maneuver). This contraction of expiratory chest muscles, diaphragm, abdominal wall muscles, and pelvic diaphragm exerts pressure on the digestive tract. Ventilation at this point temporarily ceases as the lungs push the chest diaphragm down to exert the pressure. Thoracic blood pressure rises and as a reflex response the amount of blood pumped by the heart decreases. Death has been known to occur in cases where defecation causes the blood pressure to rise enough to cause the rupture of an aneurysm or to dislodge blood clots (see thrombosis). Also, in releasing the Valsalva maneuver blood pressure falls; this, coupled with standing up quickly to leave the toilet, can result in a blackout.[citation needed] [3]

When defecating, the external sphincter muscles relax. The anal and urethral sphincter muscles are closely linked. Experiments by Dr. Harrison Weed at the Ohio State University Medical Center have shown they can only be contracted together, not individually, and that both show relaxation during urination[citation needed]. This explains why defecation is frequently accompanied by urination.

Voluntary and involuntary control[edit]

Defecation may be involuntary or under voluntary control.  Young children learn voluntary control through the process of toilet training.  Once trained, loss of control called fecal incontinence, may be caused by physical injury, nerve injury, prior surgeries (such as an episiotomy), constipation, diarrhea, loss of storage capacity in the rectum, intense fright, inflammatory bowel disease, psychological or neurological factors, or death.[4]

Anal cleansing[edit]

Main article: Anal cleansing

The anus and buttocks may be cleansed after defecation with toilet paper, similar paper products, or other absorbent material. In many cultures, e.g. in Muslim culture, water is used for anal cleansing, either in addition or exclusively.


The positions and modalities of defecation are culture-dependent. The natural and instinctive method used by all primates, including humans, is the squatting position. Squat toilets are still used by the vast majority of the world, including most of Africa, Asia and the Middle East.[5] The widespread use of sit-down toilets in the Western world is a recent development, beginning in the 19th century with the advent of indoor plumbing.[6]

Bockus' Gastroenterology, the standard textbook on the subject, states: "The ideal posture for defecation is the squatting position, with the thighs flexed upon the abdomen. In this way the capacity of the abdominal cavity is greatly diminished and intra-abdominal pressure increased, thus encouraging the expulsion of the fecal mass."[7]

Society and culture[edit]

Mythology and tradition[edit]

The caganer is a defecating figurine in Spanish Nativity scenes

Some peoples have culturally significant stories in which defecation plays a role. In a Wemale and Alune legend from the island of Seram, Maluku Province, Indonesia, the mythical girl Hainuwele defecates valuable objects.[8] One of the traditions of Catalonia (Spain) relates to the Caganer, a figurine depicted in the act of defecation appearing in nativity scenes in Catalonia and neighbouring areas with Catalan culture. The exact origin of the Caganer is lost, but the tradition has existed since at least the 18th century.[9]

See also[edit]


  1. ^ "A description of Normal Bowel Movements". 30 September 2013. Retrieved 29 November 2013. 
  2. ^ NIH. "Bowel Movement". Medline. Retrieved 13 September 2014. 
  3. ^ [Cardio-vascular Events at Defecation: Are They Unavoidable? - Medical Hypotheses, Jul 1990, 32(3):231-3]
  4. ^ "Fecal incontinence - Causes". Mayo Foundation for Medical Education and Research. Retrieved 9 September 2014.  |first1= missing |last1= in Authors list (help)
  5. ^ Kira A. The Bathroom. Harmondsworth: Penguin, 1976, revised edition, pp.115,116.
  6. ^ A History of Technology, Vol.IV: The Industrial Revolution, 1750-1850. (C. Singer, E Holmyard, A Hall, T. Williams eds) Oxford Clarendon Press, pps. 507-508, 1958
  7. ^ Bockus (1964). Gastroenterology (2nd ed.). Philadelphia and London: Saunders. p. 754. 
  8. ^ The Oxford Companion to World Mythology - Hainuwele
  9. ^ "A traditional Nativity scene, Catalan-style". BBC News. 23 December 2010. Retrieved 23 December 2010. 

Further reading[edit]

  • Deeb, Benjamin (2004). Healthy to the Core: How to Measure Effective Defecation. Greenwood Press.
  • Widmaier, Raff & Strang (2006). Vanders' Human Physiology, the mechanisms of body function. Chapter 15. McGraw Hill.
  • Cardio-vascular Events at Defecation: Are They Unavoidable? - Medical Hypotheses, Jul 1990, 32(3):231-:

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The Guardian

The Guardian
Tue, 24 Nov 2015 07:30:00 -0800

Even among those working in the field, we constantly hide behind clean-sounding words like sanitation, latrine, Wash [water sanitation and hygiene], open defecation. These words don't mean anything to the masses, so how can we drive action if we can't ...
Thu, 26 Nov 2015 05:30:00 -0800

The Ministry of Local Government and Rural Development (MLGRD) says it is helping households to get more toilet facilities towards eradicating open defecation, a major health menace across the country. Deputy sector Minister, Edwin Nii Lantey ...
Tue, 24 Nov 2015 21:26:15 -0800

"About 70% of Nigeria's population practice open defecation." This was revealed by Director, Quality Control and Sanitation of the Ministry of Water Resources, Mr Samuel Ome in a National Stakeholders workshop on the Development of National Hygiene ...

Huffington Post

Huffington Post
Fri, 20 Nov 2015 08:07:30 -0800

Last year, Prime Minister Narendra Modi launched the Swachh Bharat Abhiyan (Clean India Mission) focusing at getting rid of open defecation and installing smart waste management systems for both solid and liquid waste with an aim to free India of ...
The Hindu
Thu, 19 Nov 2015 16:06:33 -0800

Speaking on the occasion, he congratulated the villagers for the determination to make the village open defecation free. The government extended Rs.12,000 as incentive for construction of toilets. Under the State Balanced Growth Fund, the State ...

DailyPost Nigeria

Inter Press Service
Thu, 19 Nov 2015 14:42:04 -0800

The UN children's agency UNICEF says lack of sanitation, and particularly open defecation, contributes to the incidence of diarrhoea and to the spread of intestinal parasites, which in turn cause malnutrition. “We need to bring concrete and innovative ...

The Guardian

The Guardian
Thu, 12 Nov 2015 07:18:00 -0800

Children defecate into the Duo River in Liberia. Open defecation can lead to contaminated water sources and the spread of diseases. But abolishing it will require more than just access to clean toilets. Photograph: Ahmed Jallanzo/EPA ...
Sun, 22 Nov 2015 07:00:00 -0800

The Sekondi Takoradi Metropolitan Assembly (STMA) has provided over 28,013 household latrines as a measure to curb open defecation and improve general sanitation in the metropolis. Mr Mohammed Sulley, Metropolitan Environmental Officer, told the ...

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