A sphincter is a muscle that can completely close off a hollow organ located in front of or behind it. Its function is controlled automatically, so there is little that can be done consciously to influence it. Sphincters occur in the human body, for example, in the eye, at the stomach outlet or at the anus.
What is the sphincter muscle?
By a sphincter, as the name suggests, physicians understand a muscle that completely closes off a hollow organ. In this way, forward or backward flow of fluids, air or other substances is prevented. There are a total of nine sphincters in the human body. These cannot be controlled voluntarily, or only to a very limited extent. If a sphincter muscle is restricted in its function, uncontrolled leakage or flowing around of liquids can occur, for example. This can lead to conditions that are sometimes unpleasant, sometimes even dangerous to health, and often irreparable. Sphincters can be impaired in their function for a wide variety of reasons, including injury or disease, or even pregnancy or childbirth.
Anatomy and structure
Sphincters are composed of smooth muscle. For this reason, their function is automatic and cannot be controlled consciously or hardly at all. However, some muscles, such as the external sphincter at the rectum, can be voluntarily contracted. Sphincter muscles are characterized by the fact that they are closed in the resting state and thus ensure that the organs in front of or behind them remain “tight”. They can, for example, be transversely striped muscles (e.g. around the urethra) or muscle cuffs (at the anus). Alternatively, they can also be arranged in a ring shape. In some cases, they are also skeletal muscles, which are actually characterized by the fact that they can only be controlled voluntarily. However, in individual cases, such as the cardiac muscle, conscious control is not possible here either, which qualifies them for use as sphincters.
Functions and tasks
The function of each sphincter is decided by its area of use. In the human eye, for example, the sphincter pupillae muscle causes constriction of the pupil. The so-called esophageal orifice is located at the entrance to the esophagus and ensures that no air is swallowed when speaking or breathing and, on the other hand, that no stomach contents can be inhaled. The pylorus, located at the stomach outlet, regulates the transport of food from the stomach to the intestine behind it. It ensures that the food is not passed on until it has been pre-digested appropriately and there is sufficient space in the intestine. The internal and external anal sphincters ensure that bowel emptying only takes place when it is desired. The latter can be influenced at will, even if only for a certain period of time. Around the urethra is the urethralis muscle, which, like the anal sphincters, ensures that no urine escapes. Only slackening of this muscle ring coupled with increased activity of the muscles around the urinary bladder results in subsequent bladder emptying.
Diseases and complaints
If a sphincter muscle is no longer functional or functions only to a limited extent, this has consequences for the affected person that usually become noticeable within a very short time. If the muscle between the esophagus and stomach no longer closes properly, stomach acid can rise into the esophagus and damage it in the long term. As a result, inflammation or later esophageal cancer can occur. Damage to the sphincter muscles in the anal area is usually perceived as particularly unpleasant, as it leads to fecal incontinence. This problem can also be caused by childbirth, for example, which can result in a perineal tear. Urinary incontinence is also a common problem, in which uncontrolled passing of urine occurs. In some cases, pelvic floor training specially designed for this purpose can provide relief, as it can strengthen the muscles. For many patients, such problems with defecation or urination are an embarrassing and sensitive issue. Nevertheless, if in doubt, they should not be afraid to consult a doctor.
