The temporalis muscle plays an important role in the complex movements of the jaw. Located on the side of the head, this muscle is a primary component for chewing (mastication). Understanding its specific anatomical connections clarifies how these movements are generated.
What is the Temporalis Muscle?
The temporalis muscle is a broad, fan-shaped muscle on each side of the head, covering a significant portion of the temporal bone. It is a muscle of mastication, facilitating jaw movement. It fills the temporal fossa, a depressed area on the side of the skull, and can be felt and sometimes seen contracting when the jaw clenches. Its fibers run in various directions, contributing to its actions.
Origin of the Temporalis Muscle
The temporalis muscle originates from a wide area on the skull. Its primary attachment point is the temporal fossa, a broad, shallow depression on the cranium. This fossa is formed by parts of the frontal, parietal, temporal, and sphenoid bones. The muscle’s origin extends across the entire surface of this fossa, below the temporal line.
Fibers of the temporalis muscle also arise from the deep surface of the temporal fascia. This fascia is a fibrous sheet covering the muscle. These broad origin points allow the muscle to gather many fibers, which converge downwards.
Insertion of the Temporalis Muscle
The fibers of the temporalis muscle converge into a thick tendon as they descend. This tendon passes medially, underneath the zygomatic arch. The zygomatic arch is the bony prominence that forms the cheekbone. After passing beneath this arch, the tendon inserts onto the coronoid process of the mandible.
The coronoid process is a thin, triangular projection extending upward from the ramus of the mandible (lower jawbone). Its insertion extends beyond the tip of this process, down the medial surface and anterior border of the mandibular ramus, sometimes reaching near the last molar tooth. This broad insertion provides a strong anchor point for the muscle’s actions.
How Attachments Drive Muscle Action
The temporalis muscle’s origin and insertion points directly enable its actions on the lower jaw. When the muscle contracts, its fibers pull the mandible towards its origin on the skull. The anterior fibers, running more vertically, elevate the mandible, closing the mouth. This action is for biting and chewing.
The posterior fibers, with a more horizontal orientation, retract the mandible. This action pulls the jaw backward. Coordinated contraction of these fiber groups allows for the precise movements required for mastication, demonstrating how its attachments facilitate its functional capabilities.