noun a ring-like muscle that normally maintains constriction of a natural body passage or orifice and that relaxes as required by normal physiological functioning
In anatomy, a sphincter is a ring-like muscle that constricts a passage or closes a natural opening in the body. For example, the anal sphincter controls the opening and closing of the anus.
In dentistry, the anal sphincter is sometimes referenced in relation to the muscles around the mouth that control oral functions such as chewing and swallowing.
In ophthalmology, the pupillary sphincter is a muscle in the eye that constricts the pupil in response to bright light, helping to regulate the amount of light entering the eye.
In gastroenterology, sphincters play a crucial role in regulating the flow of substances through various parts of the digestive system. The lower esophageal sphincter, for instance, prevents stomach acid from flowing back into the esophagus.
In urology, sphincters are important for controlling the flow of urine through the urinary tract. The urinary sphincter, for example, helps to maintain continence by holding urine in the bladder until it is ready to be expelled.
In medical writing, a writer may discuss the function or dysfunction of the anal sphincter in relation to certain medical conditions or procedures.
Psychologists may use the term 'sphincter' in the context of psychosomatic disorders or in discussing the mind-body connection.
Medical doctors may refer to the sphincter muscles in various parts of the body when discussing anatomy, physiology, or medical procedures.
Physical therapists may work with patients who have issues with sphincter control as part of their rehabilitation process.