masseterspier

Masseterspier, or the masseter muscle, is a thick muscle of mastication located in the cheek region. It is one of the primary muscles responsible for elevating the mandible to close the mouth and for chewing. The muscle has two parts, a superficial and a deep head, forming much of the lateral cheek wall.

Origin and insertion: The masseter originates from the inferior border and medial surface of the zygomatic arch. Its fibers run downward and forward to insert on the lateral surface of the mandible, primarily at the ramus and angle. The superficial head generally attaches to the lower portion of the ramus, while the deep head attaches higher on the ramus near the coronoid process.

Innervation and blood supply: The masseter is innervated by the masseteric nerve, a branch of the mandibular division (V3) of the trigeminal nerve. Its blood supply comes from the masseteric artery, a branch of the maxillary artery. The muscle lies along the lateral aspect of the mandible and is overlapped anteriorly by the parotid gland in its relation to surrounding structures.

Function and role: The primary action of the masseter is to elevate the mandible, closing the jaw. It also contributes to protrusion and, together with the temporalis and medial pterygoid, aids in grinding movements during chewing.

Clinical relevance: Masseteric hypertrophy can occur with bruxism, clenching, or dental malocclusion and may manifest as facial swelling or jaw discomfort. Evaluation is typically clinical, with imaging if pathology is suspected. Treatments range from conservative approaches to botulinum toxin injections to reduce bite force in cosmetic or therapeutic contexts; surgical reduction is rare and reserved for refractory cases.