Muscles That Guard Entrances and Exits of Internal Passageways Are

Question

Muscles that guard entrances and exits of internal passageways are ________ muscles.
A) parallel
B) convergent
C) pennate
D) bipennate
E) circular

Accepted Answer

Circular muscles, also known as sphincter muscles, are found in the body at various locations and guard entrances and exits of internal passageways. They form a circular ring around an opening and contract to close the opening, helping to regulate the flow of substances such as food, urine, or feces. Examples include the anal sphincter, the pyloric sphincter in the stomach, and the iris sphincter in the eye.