Anatomy & Physiology Gastrointestinal #10


Which bodily sphincter allows an individual to control the release of stool?


  1. Esophageal sphincter
    • Rationale:

      The lower esophageal sphincter is a bundle of muscles at the lower end of the esophagus, where it meets the stomach. This sphincter, not under voluntary control, prevents acid and stomach contents from traveling backwards from the stomach back into the esophagus.

  2. Cardiac sphincter
    • Rationale:

      The cardiac sphincter is a synonym for the lower esophageal sphincter which prevents the backflow of acid and stomach contents from the stomach to the esophagus.

  3. Pyloric sphincter
    • Rationale:

      The pyloric sphincter is at the junction between the pylorus of the stomach and the duodenum of the small intestine. It plays an important role in digestion as it acts as a valve to control the flow of partially digested food from the stomach to the small intestine.

  4. Anal sphincter
    • Rationale:

      The anal sphincter is comprised of a group of muscles at the end of the rectum that surrounds the anus. Its function is to control the release of stool which maintains continence.


A sphincter is defined as the annular muscle surrounding, and able to contract (i.e., close), an opening in the body.


Learning Outcomes

Sphincters prevent reflux of substances held with a lumen. Smooth muscle sphincters are found at the gastroduodenal, gastroesophageal, and ileocolonic junctions, the opening of the bile duct, and at the termination of the large intestine in the recto-sigmoid region of the large intestine. The anal sphincters (e.g., internal and external) are a group of muscles at the end of the rectum that surrounds the anus thereby controlling the release of stool.

Test Taking Tip

Consider the structure and function of the choices to correctly answer this question.

Video Rationale