Muscles of Mastication
Original Editor - Olajumoke Ogunleye
Top Contributors - Olajumoke Ogunleye, Wendy Walker, Joao Costa, Kim Jackson, Vidya Acharya, Areeba Raja and Ahmed M Diab
Introduction and Overview[edit | edit source]
- The muscles of mastication are a group of muscles responsible for the chewing movement of the mandible at the temporomandibular (TMJ) joint, they enhance the process of eating, they assist in grinding food, and also function to approximate the teeth.
- The four main muscles of mastication originate from the surface of the skull and they attach onto the rami of the mandible at the TMJ.
- The movement performed by these muscles is elevation, depression, protrusion, retraction, and side to side movement.
- Unlike the muscles of facial expression that are innervated by the facial nerve (CN VII), the muscles of mastication are innervated by motor branches of the mandibular division of the trigeminal nerve (CNV3), while the main arterial supply is derived from branches of the maxillary artery.
Description[edit | edit source]
The muscles of mastication can be divided into the primary muscles and secondary or accessory muscles. The primary muscles include:
- Masseter
- Temporalis
- Lateral pterygoid
- Medial pterygoid
The secondary or accessory muscles are:
- Buccinator
- Suprahyoid muscles (digastric muscle, mylohyoid muscle, and geniohyoid muscle)
- Infrahyoid muscles (the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscle)
We will examine the muscles separately.
Masseter[edit | edit source]
It is a rectangular muscle that covers most of the lateral aspect of the ramus. It consists of three layers which blend anteriorly. They are the superficial layer, intermediate layer, and deep layer.
Origin and Insertion[edit | edit source]
The fibres of the muscle originate from the inferior zygomatic arch and the anterior two-thirds of the zygomatic arch with a connection to the posterior aspect of the zygomatic bone. The firers converge inferiorly forming a tendon that inserts at the outer surface of the mandibular ramus and the coronoid process of the mandible.
Nerve and blood supply[edit | edit source]
It is innervated by the masseter muscle from the masseteric nerve which is a branch of the mandibular nerve. Its blood supply is derived from the masseteric artery, which emerges from the maxillary artery.
Function[edit | edit source]
- The major function of the masseter muscle is to elevate the mandible, approximate the teeth.
- The intermediate and deep muscle fibres of the masseter function to retract the mandible and the superficial fibres function to protrude the mandible.
Temporalis
It is a fan-shaped muscle that fills the temporal fossa, with anterior fibers that have a vertical orientation, mid fibres have an oblique orientation, and posterior fibres have more of a horizontal orientation.
Origin and Insertion
It originates from the temporal fossa to the inferior temporal line of the lateral skull. The temporalis muscle fibres converge inferiorly forming a tendon that exists the temporal fossa passing underneath the zygomatic arch and inserting on the coronid process of the mandible.
Nerve and blood supply
It is supplied by deep temporal nerve which is a branch from anterior division of mandibular nerve.
Blood supply of the temporalis muscle is from the deep temporal part of maxillary artery and middle temoporal branches of superficial temporal artery.
