Sternohyoid muscle action is to?

Sternohyoid muscle action is to?

• A. Origin: clavicle and manubrium of sternum
• B. Insertion: hyoid bone
• C. Action: depresses larynx and hyoid bone
• D. Action: elevates mandible

Answer: (C)

The important idea is how infrahyoid muscles control the position of the hyoid and larynx. The sternohyoid, when it contracts, pulls the hyoid bone downward and, because the hyoid is linked to the larynx, helps lower the larynx as well. This fits its role after swallowing, when other muscles have lifted the hyoid and larynx and the sternohyoid brings them back toward a resting position. It originates from the sternum (and clavicle area) and inserts into the lower part of the hyoid bone, which is exactly how its shortening would pull the hyoid downward. It does not elevate the mandible—that action is carried out by muscles of mastication like the masseter and temporalis—so that option isn’t describing the sternohyoid’s function.

The important idea is how infrahyoid muscles control the position of the hyoid and larynx. The sternohyoid, when it contracts, pulls the hyoid bone downward and, because the hyoid is linked to the larynx, helps lower the larynx as well. This fits its role after swallowing, when other muscles have lifted the hyoid and larynx and the sternohyoid brings them back toward a resting position. It originates from the sternum (and clavicle area) and inserts into the lower part of the hyoid bone, which is exactly how its shortening would pull the hyoid downward. It does not elevate the mandible—that action is carried out by muscles of mastication like the masseter and temporalis—so that option isn’t describing the sternohyoid’s function.