Sphincter

Definition

A sphincter is a circular muscle that surrounds and can close a bodily passage or opening. It usually acts to regulate the flow of substances within the digestive system.

5 Must Know Facts For Your Next Test

1. The lower esophageal sphincter prevents stomach acid from entering the esophagus.
2. The pyloric sphincter controls the passage of partially digested food from the stomach to the small intestine.
3. There are both voluntary and involuntary sphincters in the human body.
4. Sphincters play a crucial role in controlling the flow of digestive juices and waste products.
5. The anal sphincter is responsible for controlling defecation.

Review Questions

• What is the primary function of a sphincter in the digestive system?
• Name two specific sphincters involved in digestion and their respective functions.
• How do voluntary and involuntary sphincters differ in their control mechanisms?

Related terms

Peristalsis:

A series of wave-like muscle contractions that move food through the digestive tract.

Gastroesophageal Reflux Disease (GERD): A condition where stomach acid frequently flows back into the esophagus, often due to a weakened lower esophageal sphincter.

Pylorus: The region of the stomach that connects to the duodenum, regulated by the pyloric sphincter.