Sphincter muscle

Sphincter Muscle

The sphincter muscle is a circular muscle that normally maintains constriction of a natural body passage or orifice and which 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.

Types of Sphincter Muscles

There are two types of sphincter muscles: Anatomical sphincter and Functional sphincter.

Anatomical Sphincter

An anatomical sphincter is a muscle that encircles an orifice (an opening) or lumen (a cavity). When it contracts, it closes the orifice. Examples include the esophageal sphincter and the anal sphincter.

Functional Sphincter

A functional sphincter refers to a section of the body that acts like a sphincter but does not have the distinct structure of an anatomical sphincter. Examples include the pyloric sphincter and the lower esophageal sphincter.

Function of Sphincter Muscles

Sphincter muscles control the passage of liquids and solids. They are responsible for the release of urine and feces, the control of blood flow, and even the dilation and constriction of the pupils in the eyes.

Medical Conditions Related to Sphincter Muscles

There are several medical conditions related to the malfunctioning of sphincter muscles. These include Achalasia, Gastroesophageal reflux disease (GERD), Fecal incontinence, and Urinary incontinence.

See Also

• Muscular system
• Digestive system
• Urinary system

References

Sphincter muscle Resources
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