Temporalis Muscle | An Overview

Mahmud Hassan, Dan Washmuth
  • Author
    Mahmud Hassan

    Mahmud has taught science for over three years. He holds a Master's of Science from the Central University of Punjab, India. He is also an assessment developer and worked on various STEM projects.

  • Instructor
    Dan Washmuth

    Dan has taught college Nutrition and Anatomy courses for several years. He has a B.S. in Exercise Physiology from Furman University and a M.S. in Dietetics & Nutrition from Florida International University. He is a Registered Dietitian (RD) and a Certified Exercise Physiologist (EP-C)

Learn to define the temporalis muscle. Learn the location, origin, and insertion of the temporalis muscle. Learn about the function and innervation of the muscle. Updated: 12/27/2021

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Temporalis Muscle

The temporalis muscle is a thin, but broad muscle. The shape of the temporalis muscle is like that of a fan. This muscle is sometimes referred to as the temporal muscle. The anterior portion of the temporalis muscle is made up of vertically oriented fibers; while the middle portion consists of obliquely oriented fibers. The posterior portion has fibers with a horizontal orientation.

Along with the masseter, lateral pterygoid, and medial pterygoid muscles, the temporalis muscle belongs to the masticatory muscle group. This muscle plays a very important role in mastication, as it works to allow the movements of the mandible— or lower jaw—at the temporomandibular joint. These movements help in biting and mastication—or mechanical breakdown—of the food, with the help of teeth in the mouth. The anterior fibers of the muscle help the lower jaw move dorsocranially; however, its posterior portion is helpful in pulling the lower jaw posteriorly. Due to this supportive influence of temporalis muscle fibers, the mandible can elevate and retract to facilitate the act of mastication.

Temporalis Origin and Insertion

The temporalis muscle is located within the temporal fossa. The temporal fossa is a depression, or indented area, within the temporal bone of the skull. This muscle generally fills most of the fossa present on both sides of the skull.

The point of origin of the temporalis muscle bridges the whole surface of the temporal fossa that is usually located below the temporal line. However, some of its fibers also arise from the temporal fascia, which lies under the skin and covers the temporal bone.

The vertically-directed anterior fibers and horizontally-directed posterior fibers of the temporalis muscle converge together onto a tendon that extends downward to the zygomatic arch. This narrow tendon further attaches onto the apex, medial surface, and anterior portion of the coronoid process of the mandible. The tendon also attaches on the anterior border of the ascending part of the ramus of the mandible in such a way that this tendon appears nearly as far forward as an individual's last molar tooth.

Labeled diagram of the lower jaw

A well-labeled diagram of the mandible or lower jaw is shown. The coronoid process and ramus are the parts of the mandible that serve as insertion points of the temporalis muscle.

Temporalis Function

The temporalis muscle is considered the strongest muscle associated with the temporomandibular joint. It is also the primary muscle that serves to retract the mandible. The main function of the temporalis muscle is chewing, which is facilitated by the contractions of its fibers. This muscle is also helpful in the biting process. When the anterior fibers of the temporalis muscle contract, it facilitates elevation—or dorsocranial movements—of the mandible. However, the contraction of its posterior fibers causes the mandible to move backward in retraction. Along with the closing of the mouth, these actions also help in the approximation of teeth. In addition to elevation and retraction, the side-to-side movements of the mandible are facilitated when the temporalis muscle contracts unilaterally.

Temporalis Muscle Innervation

The process in which the brain sends the electrical impulses to the temporalis muscle through a network of nerves is known as innervation. The cranial nerve V is mainly responsible for carrying the electrical impulses from the brain to the temporalis muscle, and thus, controls the functioning of the temporal muscle. The trigeminal nerve is another name for the cranial nerve V. It is the largest and most complex nerve of the 12 cranial nerves of humans.

Cranial nerves in humans

Illustration showing 12 cranial nerves in humans. The trigeminal (V) nerve mainly innervates the temporalis muscle.

The trigeminal nerve further divides into three large branches, which include the mandibular, the maxillary, and the ophthalmic branch. Each branch of the nerve carries the sensory signals, respectively, from the lower, middle, and upper portions of the face to the brain. The mandibular division of the trigeminal nerve carries the sensory signals from the mucous membrane of the cheek and mouth, side of the head and scalp, two-thirds of the tongue's anterior portion, the skin of the mandible, lower teeth, meninges of the anterior, and the middle cranial fossae. Thus, the temporalis muscle is more specifically innervated by the mandibular branch of cranial nerve V. The maxillary division innervates the skin of the lower eyelid, the alar part of the nose, the prominence of the cheek, the upper lip, the maxilla (upper jaw), and a part of the temple. The ophthalmic division of the trigeminal nerve is responsible for innervating various eye structures, including the cornea, conjunctiva, lacrimal gland, and ciliary body. In addition, the part of the mucous membrane of the nasal cavity and the skin of eyebrows, eyelids, nose, and forehead are also supplied through the ophthalmic branch of the trigeminal nerve.

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Frequently Asked Questions

What is the primary action of the temporalis?

The temporalis muscle is primarily responsible for facilitating the act of mastication. This muscle, inserted into the coronoid process and ramus of the mandible, helps the lower jaw to move up, backward, and side-to-side at the temporomandibular joint. These movements collectively help in biting and chewing food in the mouth.

What movement does the temporalis muscle cause?

The temporalis muscle causes elevation, retraction, and side-to-side movements of the mandible. Anterior fibers of this muscle contract, facilitating dorsocranial movements of the mandible; while the contraction of posterior fibers causes retraction, or backward movement, of the mandible. Unilateral contraction of the temporalis muscle produces side-to-side movements of the lower jaw.

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