Digestive Health Irritable Bowel Syndrome All About All of the Sphincters in Your Body By Barbara Bolen, PhD Barbara Bolen, PhD Twitter Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome. Learn about our editorial process Updated on January 23, 2022 Learn more</a>." data-inline-tooltip="true"> Medically reviewed Verywell Health articles are reviewed by board-certified physicians and healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Robert Burakoff, MD, MPH Medically reviewed by Robert Burakoff, MD, MPH LinkedIn Robert Burakoff, MD, MPH, is board-certified in gastroentrology. He is the vice chair for ambulatory services for the department of medicine at Weill Cornell Medical College in New York, where he is also a professor. He was the founding editor and co-editor in chief of Inflammatory Bowel Diseases. Learn about our Medical Review Board Print Table of Contents View All Table of Contents Digestive Sphincters Other Sphincters Sphincters are special, circular muscles that open and close certain body parts. Most often, the sphincter regulates the passage of some type of fluid, such as bile, urine, or fecal matter. The action of sphincters may happen involuntarily through the autonomic nervous system or maybe under some voluntary control through the somatic nervous system. If a sphincter loses muscle tone or has too much tone (spasticity), symptoms and illness can follow. This can include urinary retention, in which the bladder can't empty completely. Sphincter issues can also cause bladder and fecal incontinence, or the inability to control the bladder or bowels. This article discusses some of the different sphincters in the body, where they're located, and what they do. BSIP / UIG / Getty Images Digestive System Sphincters There are six different sphincters within the digestive system. Upper Esophageal Sphincter The upper esophageal sphincter (UES) is also known as the inferior pharyngeal sphincter. It can be found at the end of the pharynx (throat). It protects the entrance to the esophagus, which carries food from your throat to your stomach. The UES prevents air from getting into the esophagus when you breathe. It also prevents you from breathing food into your respiratory tract. Because of its location, the UES also plays a role in burping and vomiting. Malfunctioning of the UES, as part of gastroesophageal reflux disease (GERD), can cause acid to back up into the throat or into the airways. The Upper Esophageal Sphincter and Acid Reflux Lower Esophageal Sphincter The lower esophageal sphincter (LES), also known as the cardiac sphincter, is located at the bottom of the esophagus where it meets up with the stomach. It lets food pass from the esophagus into the stomach and allows air to escape from the stomach when burping. It also prevents stomach acid from washing back up into the esophagus. A malfunction of the LES is one of the primary causes of GERD. Recap The upper esophageal sphincter prevents air from getting into the esophagus and keeps food from going into your respiratory tract. The lower esophageal sphincter lets air come up from the stomach when burping and usually keeps stomach acid out of the esophagus. 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 to allow partially digested food (chyme) to pass from the stomach into the duodenum. This allows for further digestion and absorption of nutrients into the body. Sphincter of Oddi Sphincter of Oddi (SO) is located where the common bile duct and the pancreatic duct connect to the duodenum. The common bile duct is a tube that carries bile into the duodenum. The pancreatic duct carries digestive enzymes to the duodenum. The SO opens after you've eaten to allow bile from the gallbladder and enzymes from the pancreas to enter the duodenum. This breaks down food components for absorption into the body. Sphincter of Oddi dysfunction (SOD) happens when this sphincter doesn't work correctly. This causes a backup of bile and pancreatic enzymes. A relatively rare disorder, it can cause episodes of pain in the chest area. Sphincter of Oddi Anatomy and Function Ileocecal Sphincter The ileocecal sphincter is located where the small intestine and the large intestine meet. There is not much known about this sphincter. However, it is thought to expel chyme from the end of the small intestine (the ileum) into the large intestine. Anal Sphincter The anal sphincter is located at the end of the rectum, and therefore at the end of the digestive tract. The anal sphincter regulates the process of the evacuation of stool. It has both an inner and outer component. The inner sphincter is under involuntary control and therefore prevents stool from leaking out. The outer sphincter is predominantly under voluntary control and allows for a bowel movement. A malfunction of the anal sphincter can cause stool leakage, a health condition known as fecal incontinence. Recap The inner part of the anal sphincter keeps stool from leaking out. The outer portion allows you to have a bowel movement. Anal Sphincter Anatomy and Function Other Sphincters There are other sphincters that you have throughout your body. Urethral Sphincter Also known as the sphincter urethrae, this sphincter controls the holding and emptying of urine. Like the anal sphincter, the urethral sphincter has both inner and outer muscles. The inner muscle has involuntary control and the outer muscle has voluntary control. Iris Sphincter The iris sphincter is also known as the pupillary sphincter or sphincter pupillae. This sphincter regulates the closing of the pupil in the eye. Summary The body's sphincters are circular muscles that open and close certain parts of the body. Sphincters in the digestive tract open to allow food, bile, or digestive enzymes to go from one part of the body to another. In some cases, the sphincter may not function correctly. This can cause symptoms or illness. For instance, if the lower esophageal sphincter doesn't work right, it can let stomach acids into the food pipe, leading to GERD. Sphincters are in other parts of the body as well. They include the urethral sphincter, which can control the flow of urine, and the iris sphincter, which can constrict your pupils. Frequently Asked Questions What is a sphincter? Sphincters are circular 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 fluid and food from the mouth to the stomach, through the intestines, and out the anus. In the eye, the pupillary sphincter in the iris opens and closes to regulate the amount of light it lets in. How many sphincters are there in the human body? A lot. There are at least 50 or 60 different types of sphincters in the human body. Some are microscopic, such as the millions of precapillary sphincters in the circulatory system. Some are controlled involuntarily by the autonomic nervous system, some respond to certain stimuli, and others we control directly.The anus has two sphincters, an internal involuntary sphincter and an external voluntary sphincter that we control. What health problems are related to sphincters? Sphincter muscles can become weak or damaged, resulting in health conditions. In gastroesophageal reflux disease (GERD), the lower esophageal sphincter muscle relaxes at the wrong time. This allows stomach acid to flow up the esophagus, causing acid reflux. If the anal sphincter is weak and damaged, it can cause fecal incontinence. Was this page helpful? Thanks for your feedback! One of the most challenging aspects of having IBS is trying to figure out what's safe to eat. Our recipe guide makes it easier. Sign up and get yours now! Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 6 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Feki A, Faltin DL, Lei T, Dubuisson JB, Jacob S, Irion O. Sphincter incontinence: is regenerative medicine the best alternative to restore urinary or anal sphincter function? Int J Biochem Cell Biol. 2007;39(4):678-84. doi:10.1016/j.biocel.2006.11.001 Perry KA, Banerjee A, Melvin WS. Radiofrequency energy delivery to the lower esophageal sphincter reduces esophageal acid exposure and improves GERD symptoms: a systematic review and meta-analysis. Surg Laparosc Endosc Percutan Tech. 2012;22(4):283-8. doi:10.1097/SLE.0b013e3182582e92 Baillie J. Sphincter of Oddi dysfunction. Curr Gastroenterol Rep. 2010;12(2):130-4. doi: 10.1007/s11894-010-0096-1 Rezvan A, Jakus-waldman S, Abbas MA, Yazdany T, Nguyen J. Review of the diagnosis, management and treatment of fecal incontinence. Female Pelvic Med Reconstr Surg. 2015;21(1):8-17. doi:10.1097/SPV.0000000000000102 Mayo Clinic. Gastroesophageal reflux disease. Markland AD, Dunivan GC, Vaughan CP, Rogers RG. Anal intercourse and fecal incontinence: Evidence from the 2009-2010 National Health and Nutrition Examination Survey. Am J Gastroenterol. 2016;111(2):269–74. doi:10.1038/ajg.2015.419 Additional Reading Minocha A, Adamec C. The Encyclopedia of the Digestive System and Digestive Disorders (2nd Ed.) New York:Facts on File. 2011. Mittal RK. Upper esophageal sphincter. in: Motor Function of the Pharynx, Esophagus, and its Sphincters. San Rafael (CA): Morgan & Claypool Life Sciences; 2011.