Sphincter
From late Latin sphincter, from Greek sphinkter, band, contractile muscle, from sphingein, to bind tight.
A sphincter is a ring-like muscle that normally maintains constriction of a natural body passage or orifice and that relaxes as required by normal physiological functioning.
Some examples of sphincters include:
- Anus
- Cardia, at the upper portion of the stomach
- 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.