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Mastication Muscles Anatomy
Mastication Muscles Anatomy
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The muscles of mastication are the four main muscles responsible for moving the lower jaw (mandible) at the temporomandibular joint (TMJ).
These movements allow us to chew, speak, and grind food.
All four muscles come from the first pharyngeal arch in development and are supplied by the mandibular branch of the trigeminal nerve (cranial nerve V3).
The four muscles are:
Masseter
Temporalis
Medial pterygoid
Lateral pterygoid.
Masseter
Masseter
The masseter is the strongest muscle used in chewing. It sits on the side of the face and covers the outer surface of the lower jaw.
It elevates the mandible - this is the primary muscle that helps you close your mouth tightly.
It has two parts (superficial and deep) that start from the zygomatic bone and zygomatic arch.
Origin: Maxilla arch; zygomatic arch.
Insertion: Ramus of the mandible.
Temporalis
The temporalis is a broad, fan-shaped muscle on the side of the head. It fills the temporal fossa and narrows into a tendon that passes under the cheekbone (zygomatic arch) to reach the mandible.
It elevates the mandible (closes the mouth) and retracts the mandible (pulls it backward), helping in precise biting.
Origin: Temporal bone.
Insertion: Ramus of the mandible.
Medial Pterygoid
Medial Pterygoid
The medial pterygoid sits on the inside of the mandible. It mirrors the masseter on the inner surface of the jaw. It elevates the mandible, helps with grinding by moving the jaw side-to-side, and contributes slightly to protrusion (moving the jaw forward).
It has two heads that originate from the sphenoid, palatine, and maxilla bones.
Inserts near the angle of the mandible.
Lateral Pterygoid
Lateral Pterygoid
The lateral pterygoid is the only masticatory muscle that primarily opens the mouth and pushes the jaw forward. It sits deeper in the face and has a horizontal fiber direction. It protrudes the mandible (moves it forward), depresses the mandible (helps open the mouth), and when used on one side, it creates side-to-side movements needed for chewing.
Two heads originate from parts of the sphenoid bone.
Inserts on the neck of the mandible and part of the TMJ disc.
Need a recap? Take a look at the Mastication Muscles anatomy notes here.
Need a recap? Take a look at the Mastication Muscles anatomy notes here.
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References
References
Gray, H. (2009). Anatomy of the human body, part 2 (LibriVox Volunteers, Narr.) [Audiobook]. LibriVox. https://librivox.org/anatomy-of-the-human-body-part-2-by-henry-gray/ (Original work published 1858)
J Gordon Betts, Desaix, P., Johnson, E., Johnson, J. E., Korol, O., Kruse, D., Poe, B., Wise, J., Womble, M. D., & Young, K. A. (2013). Anatomy & physiology. Openstax College, Rice University. https://openstax.org/details/books/anatomy-and-physiology
Based on OpenStax, Anatomy and Physiology (2013), licensed under CC BY 4.0.
Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.
Content paraphrased; adaptations were made.
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