The sphincter muscle or sphincter (m.) (Latin / Germanized to Greek σφίγγω, sfingo 'press together') is a ring-shaped muscle in vertebrate anatomy that can completely seal off a hollow muscular organ . This prevents a forward or backward flow. Most sphincter muscles consist of smooth muscles and are therefore not or only partially accessible to voluntary activity. In invertebrates , a sphincter is a muscle that closes a housing or something similar. So the sphincter pulling mussels the two shell halves together.
- The sphincter pupillae eye muscle causes the pupil to constrict .
- The orbicularis oris muscle ("circular muscle of the mouth") around the mouth opening forms the fleshy basis of the lips .
- The upper esophageal sphincter or esophageal mouth consists exclusively of (striated) skeletal muscles - essentially the pars fundiformis of the musculus constrictor pharyngis inferior . It closes the entrance to the esophagus , on the one hand to prevent the ingestion of air ( aerophagia ) while breathing and speaking and on the other hand to prevent the aspiration of stomach contents.
- The pylorus (" stomach gatekeeper ") is the sphincter muscle at the exit of the stomach .
- The papilla duodeni major ("father's papilla") acts as a sphincter in the area of the mouth of the bile duct into the duodenum (duodenum).
- The ileo-caecal valve acts as a sphincter at the transition from the small intestine to the large intestine .
- The sphincter muscles on the anus are the external and internal anal sphincter muscles ( internal ani sphincter and external ani sphincter ).
- In the urethralis muscle ("urethral muscle "), fiber strands of the transversus perinei profundus muscle lie in a ring around the pars membranacea urethrae of the urethra . The drooping ( tone reduction) enables the simultaneous increase in tone of the detrusor vesicae the micturition (urination).
- The closing mechanism of the esophagus opposite the stomach is also misleadingly referred to as the “lower esophageal sphincter”, although it does not actually involve a sphincter muscle. This “functional sphincter” is mainly formed by a constricting loop of the diaphragm .
Malfunctions of the “lower esophageal sphincter” can appear as insufficient closure or insufficient opening. If the gastric entrance is not blocked, stomach acid flows back into the esophagus (reflux) and causes reflux esophagitis . If this functional sphincter does not open, achalasia occurs .
The urinary incontinence is a generic term for various disorders of the reservoir function of the bladder and involuntary disposal of urine . In 1953 Hubert Hartl developed sphincterometry in Göttingen to assess the severity of such incontinence. Urinary incontinence should be prevented or improved through pelvic floor training .
- Frank Mannes: Changes in the motility of the esophagus after gastrectomy (dissertation at the Medical Faculty of the Martin Luther University Halle-Wittenberg, 2003)
- Ulrike Bommas-Ebert, Philipp Teubner, Rainer Voß: Short textbook anatomy and embryology . 2nd Edition. Thieme, Stuttgart 2005, ISBN 3-13-135532-8 , p. 291 f .
- Horst Kremling : Gynecological-urological borderline questions. In: Würzburger medical history reports 23, 2004, pp. 204–216; here: p. 207.