What is the action of the Masseter muscle?

What is the action of the Masseter muscle?

• A. Elevates mandible
• B. Closes jaw; elevates mandible
• C. Depresses larynx
• D. Elevates ribs

Answer: (B)

The Masseter’s main role is to close the jaw by elevating the mandible. It runs from the zygomatic arch to the mandible, so when it contracts, it lifts the lower jaw to bring the teeth together, which is the primary mechanism of biting. Its fibers can also help protrude the jaw slightly for a stronger bite, but the essential action you’re being tested on is elevating the mandible to close the mouth. Depressing the larynx and elevating ribs are actions of other muscles, not the masseter, so the description that includes both closing the jaw and elevating the mandible best matches its function.

The Masseter’s main role is to close the jaw by elevating the mandible. It runs from the zygomatic arch to the mandible, so when it contracts, it lifts the lower jaw to bring the teeth together, which is the primary mechanism of biting. Its fibers can also help protrude the jaw slightly for a stronger bite, but the essential action you’re being tested on is elevating the mandible to close the mouth. Depressing the larynx and elevating ribs are actions of other muscles, not the masseter, so the description that includes both closing the jaw and elevating the mandible best matches its function.