Sphincter
From Free net encyclopedia
A sphincter is a ring-like muscle which normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. There are at least 42 different sphincters in the human body, some of them microscopic in size.
Some examples of sphincters include:
- Iris of the human eye.
- Anus, There are two anal sphincters which control the exit of feces from the body.
- Cardia, at the upper portion of the stomach. This sphincter prevents the acidic contents of the stomach from moving upward into the esophagus.
- Sphincter urethrae, or Urethral sphincter.
- Pyloric sphincter, at the lower end of the stomach.
- Sphincter pupillae, or Pupillary sphincter, belonging to the iris in the eye.
- Sphincter of Oddi, or Glisson's sphincter, controlling secretions from the liver, pancreas and gall bladder into the duodenum.
- Orbicularis oris muscle, muscle around the mouth.
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Etymology
Etymology: from late Latin sphincter, from Greek sphinkter, band, contractile muscle, from sphingein, to bind tight. Compare Sphinx, "the strangler".
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