File:Ileocaecal_sphincter.png · Wikimedia Commons · See Wikimedia Commons
sphincter muscle
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A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the human body, some microscopically small, in particular the millions of precapillary sphincters. Sphincters relax at death, often releasing fluids and fæces.
Key facts
- Muscle.Name
- Sphincter
- Muscle.Width
- 550 px
via Wikipedia infobox
~3 min read
Encyclopedic overview
5 sectionsContents
- Functioning
- Classifications
- Examples
- References
- See also
A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the human body, some microscopically small, in particular the millions of precapillary sphincters. Sphincters relax at death, often releasing fluids and fæces.
==Functioning== Each sphincter is associated with the lumen (opening) it surrounds. As long as the sphincter muscle is contracted, its length is shortened and the lumen is constricted (closed). Relaxation of the muscle causes it to lengthen, opening the lumen and allowing the passage of liquids, solids, or gases.
Excerpted from Wikipedia’s “sphincter muscle” article, available under the CC BY-SA 4.0 licence.