Everything about all the sphincters of your body.


Sphincters are special round muscles that open and close certain parts of the body. Most often, the sphincter regulates the passage of some type of fluid, such as bile, urine, or stool.

Sphincter action can occur involuntarily through the autonomic nervous system , or possibly under some voluntary control through the somatic nervous system .

If the sphincter loses muscle tone or is too toned (spasticity), symptoms and / or diseases may appear, such as urinary retention, urinary bladder and fecal incontinence.

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Sphincters of the digestive system.

There are six different sphincters in the digestive system.

Upper esophageal sphincter

The upper esophageal sphincter (UES), also known as the lower pharyngeal sphincter, is located at the end of the pharynx where it protects the entrance to the esophagus . The UES is responsible for preventing air from entering the esophagus when we breathe and for preventing food from being absorbed into our airways.

Due to its location, CEE also plays a role in belching and vomiting. Discontinuation of the UES as part of gastroesophageal reflux disease (GERD) can cause acid to flow back into the throat or airways.

Lower esophageal sphincter

The lower esophageal sphincter (LES), also known as the cardiac sphincter, is located in the lower part of the esophagus where it meets the stomach.

Its main functions are to allow food to pass from the esophagus to the stomach, to allow air to escape from the stomach when burping, and to prevent stomach acid from returning to the esophagus. Malfunction of the LES is one of the main causes of GERD .

Pyloric sphincter

The pyloric sphincter is located between the stomach and the duodenum , which is the first part of the small intestine. The pyloric sphincter opens, allowing partially digested food (chyme) to pass from the stomach into the duodenum for further digestion and absorption of nutrients in the body.

Sphincter of Oddi

The sphincter of Oddi (SO) is where the common bile duct and pancreatic duct join the duodenum. SO opens after we eat to allow bile from the gallbladder and enzymes from the pancreas to enter the duodenum to break down food components for absorption into the body.

Sphincter of Oddi Dysfunction (SOD) , a relatively rare condition that can cause episodes of chest pain .

Ileocecal sphincter

The ileocecal sphincter is located at the intersection of the small and large intestines. Little is known about this sphincter except that it is believed to drain chyme from the end of the small intestine (ileum) into the large intestine.

Anal sphincter

The anal sphincter is at the end of the rectum and therefore at the end of the digestive tract. The anal sphincter regulates the evacuation process of stool. It has an internal and external component.

The internal sphincter is under involuntary control (and thus prevents the leakage of stool), while the external sphincter is predominantly under voluntary control, allowing for bowel movements. A malfunctioning anal sphincter can lead to loss of stool, a health condition known as fecal incontinence .

Other sphincters

There are other sphincters in your body.

Urethral sphincter

Also known as the urethral sphincter, this sphincter controls the retention and emptying of urine. Like the anal sphincter, the urethral sphincter has internal and external muscles, which, respectively, are mainly under involuntary and voluntary control.

Iris sphincter

Also known as the pupillary sphincter or sphincter pupils. This sphincter regulates the closure of the pupil in the eye.

Frequently asked questions

  • Sphincters are round muscles that serve as valves to open and close certain parts of the body.

    For example, the digestive system has several sphincters that regulate the passage of liquids and food from the mouth to the stomach, through the intestines, and out of the anus. In the eye, the pupillary sphincter of the iris opens and closes to regulate the amount of light it lets through.

  • A lots of. There are at least 50 or 60 different types of toilet bowls in the human body. Some are microscopic, like the millions of precapillary sphincters in the circulatory system. Some of them are involuntarily controlled by the autonomic nervous system, some respond to certain stimuli, and others are directly controlled.

    There are two sphincters in the anus: the involuntary internal sphincter and the voluntary external sphincter, which we control.

  • The sphincter muscles can become weak or damaged, resulting in poor health. In gastroesophageal reflux disease (GERD), the lower esophageal sphincter muscle relaxes at the wrong time. This allows acid from the stomach to flow into the esophagus and cause acid reflux. If the anal sphincter is weakened and damaged, it can lead to fecal incontinence.

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