Sphincter facts for kids
A sphincter is a circular muscle that closes off a body passage or opening and which relaxes and opens as required. Sphincters are found in many animals. There are over 60 types in the human body, some microscopically small.
Sphincters control the passage of liquids and solids. This is evident, for example, in the blowholes of numerous marine mammals.
Many sphincters are used every day in the normal course of digestion. Some examples are the lower oesophageal sphincter (or cardiac sphincter), which resides at the top of the stomach, and keeps stomach acids and other stomach contents from pushing up into the oesophagus and the anus, where there are two sphincters which control the exit of feces from the body.
Sphincter Facts for Kids. Kiddle Encyclopedia.