The posterior fibers of the temporalis primarily perform which action?

• A. Elevate
• B. Protrude
• C. Depress
• D. Retrude

Answer: (D)

Posterior fibers of the temporalis are oriented to pull the mandible backward, so their primary action is retrusion of the jaw. When these fibers contract, they draw the mandible posteriorly toward the temporal bone, helping to position the bite in a more rearward (retruded) place and stabilizing the jaw during chewing. While the temporalis as a whole can contribute to elevation, and the anterior fibers help with elevation and even protrusion in combination with other muscles, the posterior portion is specialized for pulling the jaw back. Depression of the mandible is accomplished mainly by other muscles, not the posterior temporalis. So the best answer is retrude.