Sphincter

A sphincter is a circular Muscle around a natural conduit (digestive tract, vessels…) who can dilate and contract. This mechanism makes it possible to close completely or partially an opening or a conduit of the body, and to open it when the need is felt some.

Its order can be voluntary or automatic (in reflex with certain stimulations).

Let us quote in particular:

  • the anal sphincters prevent the involuntary exit of the feces, but allow their exit at the time of the defecation;
  • the vesical sphincter plays the same part for the exit of the Urine of the Vessie, allowed at the time of the Miction;
  • the Pylore is placed in bottom of the Estomac and stops the passage of food towards the Small intestine .
  • the Cardia is placed in top of the Estomac and allows the passage of food of the Oesophage the Estomac while retaining food inside during digestion
  • the sphincters of the iris are responsible for the constriction and dilation of the Pupille.
  • the sphincters of the blood-vessels, ensure the Vasoconstriction and the Vasodilatation, phenomena which control the blood flow. They paper the external wall of the blood-vessels.
  • the lower Sphincter oesophagien separates it from the area cardiale of the stomach,
  • At the time of the death, the sphincters are slackened.

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