Editing Defecation (section)

==Description==
{{multiple image|image1=Defecating lion in Warsaw Zoo.jpg|image2=Speke's Gazelle (Gazella spekei) (5532395054).jpg|image3=Defecating bison.jpg|image4=Canis lupus (1855281790).jpg|image5=White horse defecate on field.jpg|image6=DSC 8148 (4933509680).jpg|footer=Defecation postures of [[mammal]]s|perrow=3|total_width=440px}}
[[File:Cattle_Defecating.webm|thumb|Video of a cow defecating]]
===Physiology===
{{Further|Rectum#Function}}
The [[Rectal ampulla|rectum ampulla]] stores fecal waste (also called stool) before it is excreted. As the waste fills the rectum and expands the rectal walls, 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 feces are stored until the next mass peristaltic movement of the transverse and descending colon.

When the rectum is full, an increase in pressure within the rectum 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.<ref>{{cite web |url=https://medicine.umich.edu/sites/default/files/content/downloads/bowel-function.pdf |title=Bowel Function Anatomy |publisher=University of Michigan Health System |accessdate=2021-05-19 |quote=The levator ani and the puborectalis need to coordinate properly in order to expel contents from the anal canal. }}</ref>

===Voluntary and involuntary control===

The [[external anal sphincter]] is under voluntary control whereas the [[internal anal sphincter]] is involuntary. In [[infant]]s, the defecation occurs by [[Reflex|reflex action]] without the voluntary control of the external anal sphincter. Defecation is voluntary in adults. 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, [[childbirth]], or [[death]].<ref>{{cite web|author=<!--Staff writer(s); no by-line.--> |title=Fecal incontinence - Causes|url=http://www.mayoclinic.org/diseases-conditions/fecal-incontinence/basics/causes/con-20034575|publisher=Mayo Foundation for Medical Education and Research|access-date=9 September 2014}}</ref>

Sometimes, due to the inability to control one's bowel movement or due to excessive fear, defecation (usually accompanied by urination) occurs involuntarily, soiling a person's undergarments. This may cause significant embarrassment to the person if this occurs in the presence of other people or a public place.

===Posture===
{{main article|Human defecation postures}}
The positions and modalities of defecation are [[Culture#Cultures by region|culture-dependent]]. [[Squat toilet]]s are used by the vast majority of the world, including most of Africa, Asia, and the Middle East.<ref>{{cite book|last1=Kira|first1=Alexander|title=The Bathroom|date=1976|publisher=Viking Pr|location=New York, N.Y.|isbn=978-0-670-00612-0|pages=115–116|edition=2. ed. New and expanded}}</ref> The use of sit-down [[toilet]]s in the [[Western world]] is a relatively recent development, beginning in the 19th century with the advent of indoor plumbing.<ref>{{cite book |editor1=C. Singer |editor2=E Holmyard |editor3=A Hall |editor4=T. Williams |year=1958 |orig-year=1954 |title=A History of Technology |volume=IV: The Industrial Revolution, 1750-1850 |publisher=Oxford Clarendon Press |pages=507–508 |oclc=886036895}}</ref>