Podcast
Questions and Answers
Which muscle of mastication is responsible for elevation and retraction of the mandible?
Which muscle of mastication is responsible for elevation and retraction of the mandible?
What is the main function of the masseter muscle?
What is the main function of the masseter muscle?
Which nerve innervates both the masseter and temporalis muscles?
Which nerve innervates both the masseter and temporalis muscles?
From which bone does the superficial part of the masseter muscle originate?
From which bone does the superficial part of the masseter muscle originate?
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Which muscle among the muscles of mastication is covered by tough fascia and can be harvested for myringoplasty?
Which muscle among the muscles of mastication is covered by tough fascia and can be harvested for myringoplasty?
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What is the primary function of the medial pterygoid muscle?
What is the primary function of the medial pterygoid muscle?
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Which bone does the deep head of the medial pterygoid muscle originate from?
Which bone does the deep head of the medial pterygoid muscle originate from?
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Which nerve innervates both the lateral and medial pterygoid muscles?
Which nerve innervates both the lateral and medial pterygoid muscles?
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What is NOT a function of the lateral pterygoid muscle?
What is NOT a function of the lateral pterygoid muscle?
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Which of the following muscles is considered a secondary or accessory muscle for mastication?
Which of the following muscles is considered a secondary or accessory muscle for mastication?
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Study Notes
Muscles of Mastication
The muscles of mastication are a group of muscles that work together to facilitate chewing and grinding of food. These muscles are associated with movements of the jaw (temporomandibular joint) and are all bilateral structures. They develop from the first pharyngeal arch and are innervated by branches of the trigeminal nerve (CN V), specifically the mandibular nerve. The four main muscles of mastication are:
Masseter
The masseter muscle is the most powerful muscle of mastication. It is quadrangular in shape and has two parts: a deep part and a superficial part. The superficial part originates from the maxillary process of the zygomatic bone, while the deep part originates from the zygomatic arch of the temporal bone. Both parts attach to the ramus of the mandible. The masseter muscle is responsible for elevation of the mandible (closing the mouth) and is innervated by the mandibular nerve (V 3).
Temporalis
The temporalis muscle originates from the temporal fossa, a shallow depression on the lateral aspect of the skull. It is covered by tough fascia and can be harvested surgically to repair a perforated tympanic membrane (myringoplasty). The muscle attaches to the coronoid process of the mandible and is responsible for elevation of the mandible (closing the mouth) and retraction of the mandible (moving the jaw posteriorly). It is also innervated by the mandibular nerve (V 3).
Medial Pterygoid
The medial pterygoid muscle has a quadrangular shape with two heads: superficial and deep. It is located inferiorly to the lateral pterygoid. The superficial head originates from the maxillary tuberosity and the pyramidal process of the palatine bone, while the deep head originates from the medial aspect of the lateral pterygoid plate of the sphenoid bone. Both heads attach to the ramus of the mandible near the angle of the mandible. The medial pterygoid muscle is responsible for elevation of the mandible (closing the mouth) and is innervated by the mandibular nerve (V 3).
Lateral Pterygoid
The lateral pterygoid muscle has a triangular shape with two heads: superior and inferior. It has horizontally orientated muscle fibers, making it the major protractor of the mandible. The superior head originates from the greater wing of the sphenoid, and the inferior head originates from the lateral pterygoid plate of the sphenoid. The two heads converge into a tendon that attaches to the neck of the mandible. The lateral pterygoid muscle is responsible for both bilateral protraction of the mandible and depression of the chin, as well as unilateral 'side to side' movement of the jaw. It is innervated by the mandibular nerve (V 3).
In addition to these four primary muscles, there are secondary or accessory muscles that assist in mastication, including the buccinator, suprahyoid muscles (digastric, mylohyoid, and geniohyoid), and infrahyoid muscles (sternohyoid, sternothyroid, thyrohyoid, and omohyoid). These muscles work together to ensure proper chewing, food grinding, and approximation of the teeth. The muscles of mastication are vital for the process of eating and are essential for maintaining oral health.
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Description
Explore the key muscles involved in mastication, their origins, functions, and innervation. Learn about the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles along with their roles in jaw movement and chewing. Understand the importance of these muscles for oral health and proper eating habits.
