Question

multiple choice question

muscles that form valve-like structures that control various body openings and passages are called _______

orifices
sphincters
valves
vessels

Explanation:

Analyze the question stem

The question asks for the term used to describe muscles that form circular, valve-like structures to control body openings and passages.

Evaluate the options

• orifices: These are the actual openings or holes in the body, not the muscles that control them.
• sphincters: These are circular muscles that constrict or dilate to regulate the passage of substances through body openings, acting as natural valves. This matches the definition.
• valves: While sphincters act like valves, "valves" themselves are general anatomical structures (often membranous folds, like in the heart or veins) rather than a specific class of muscle tissue.
• vessels: These are tubular structures (like blood vessels) that transport fluids, not the controlling muscular rings.

Apply anatomical concepts

Using the Anatomical Terminology knowledge point, we identify that circular muscles guarding body inlets and outlets are functionally and structurally classified as sphincters (e.g., the orbicularis oris, pyloric sphincter, or anal sphincter).

Answer:

• orifices
• sphincters (Correct answer)
• valves
• vessels