Logan Steele
The human face has about 20 main facial muscles that enable essential functions such as chewing and making facial expressions. These muscles are located all over the face, including the ears, mouth, forehead, nose, and eyes. One of the most important functions of the facial muscles is to open and close the mouth, which is primarily achieved through the movement of the jaw. The muscles responsible for closing the mouth are known as the muscles of mastication, and they consist of four main muscles: the masseter, temporalis, medial pterygoid, and lateral pterygoid. These muscles work together to produce movements such as elevation, depression, protrusion, retraction, and side-to-side movement of the mandible.
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What You'll Learn
- The medial pterygoid muscle elevates the mandible, closing the mouth
- The temporalis muscle opposes gravity to keep the mouth closed
- The masseter muscle is involved in the elevation of the mandible
- The lateral pterygoid muscle moves the mandible from side to side
- The orbicularis oris muscle closes or purses the lips
The medial pterygoid muscle elevates the mandible, closing the mouth
The human face has about 20 main facial muscles that are essential for chewing and making facial expressions. 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 and assist in grinding food.
The medial pterygoid muscle is one of the four muscles of mastication, along with the masseter, temporalis, and lateral pterygoid muscles. It has a quadrangular shape with two heads: deep and superficial. 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 innervated by the mandibular nerve (V3) and receives its principal blood supply from the pterygoid branches of the maxillary artery. Its major functions include the elevation of the mandible, resulting in the closing of the mouth, and side-to-side movements during grinding and chewing. The medial pterygoid muscle also plays a role in the protrusion of the mandible.
The mandible is the only bone that moves during mastication and other activities such as talking. The medial pterygoid muscle, along with the other muscles of mastication, work together to produce the necessary movements for chewing and speaking.
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The temporalis muscle opposes gravity to keep the mouth closed
The mouth is closed by the action of the muscles of mastication, which consist of the temporalis, masseter, medial pterygoid, and lateral pterygoid muscles. These muscles attach to the mandible and produce movements of the lower jaw at the temporomandibular joint (TMJ). The temporalis muscle, in particular, functions as an elevator of the mandible, opposing gravity to keep the mouth closed.
The temporalis muscle is a fan-shaped muscle that fills the temporal fossa, with anterior fibres that have a vertical orientation, mid fibres with an oblique orientation, and posterior fibres that are more horizontal. It originates from the temporal fossa and extends to the inferior temporal line of the lateral skull. The fibres of the temporalis muscle converge inferiorly, forming a tendon that exits the temporal fossa, passes underneath the zygomatic arch, and inserts on the coronoid process of the mandible.
The function of the temporalis muscle is largely dependent on the orientation of its fibres. The anterior and mid fibres, which are vertically and obliquely oriented, respectively, work together to elevate the mandible, opposing gravity to keep the mouth closed. On the other hand, the posterior fibres, which are horizontally oriented, function to retract the mandible, pulling the jaw backwards. Additionally, the temporalis muscle contributes to grinding movements by enabling side-to-side movements of the mandible.
The temporalis muscle is innervated by the deep temporal nerve, a branch of the anterior division of the mandibular nerve. Its blood supply comes from two sources: the deep temporal part of the maxillary artery and the middle temporal branches of the superficial temporal artery. This muscle plays a crucial role in the process of mastication, or chewing, by elevating the mandible and opposing gravity to maintain a closed mouth.
In summary, the temporalis muscle is an essential component of the muscles of mastication, primarily functioning to elevate the mandible and oppose gravity, ensuring that the mouth remains closed. Its unique structure, innervation, and blood supply enable it to work in coordination with other muscles to facilitate essential jaw movements, such as chewing and grinding food.
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The masseter muscle is involved in the elevation of the mandible
The masseter muscle is one of the four muscles responsible for the action of mastication (chewing). It is a powerful, fan-shaped, superficial quadrangular muscle that fills the temporal fossa. The masseter muscle is involved in the elevation of the mandible, causing the mouth to close.
The masseter muscle originates from the zygomatic arch and inserts along the angle and lateral surface of the mandible. 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 masseter muscle receives its motor innervation from the mandibular division of the trigeminal nerve. Its blood supply is primarily from the masseteric artery, a branch of the internal maxillary artery.
The masseter muscle has two layers that slightly differ in their attachments. Its larger, superficial layer arises from the maxillary process of the zygomatic bone and the anterior two-thirds of the inferior border of the zygomatic arch. The deep layer of the masseter muscle arises from the medial surface and inferior margin of the zygomatic arch. These fibres run vertically downwards to insert onto the upper part of the ramus of the mandible and the coronoid process.
The masseter muscle is a strong muscle that covers the lateral aspect of the ramus of the mandible. The major function of the masseter muscle is to elevate the mandible, with a minor contribution to protrusion of the mandible. The intermediate and deep muscle fibres of the masseter function to retract the mandible, and the superficial fibres function to protrude the mandible. The deep fibres are important stabilisers of the temporomandibular joint (TMJ).
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The lateral pterygoid muscle moves the mandible from side to side
The lateral pterygoid muscle is a craniomandibular muscle with two heads or bellies: the superior belly and the inferior belly. The inferior belly is three times larger than the superior belly. The muscle is located in the infratemporal fossa of the skull and is one of the four muscles of mastication. The other three muscles of mastication are the medial pterygoid, masseter, and temporalis.
The primary function of the lateral pterygoid muscle is to move the mandible forward (protrusion) and side to side. It is the only muscle of mastication that participates in depressing the mandible (opening the jaw). The unilateral contraction of the lateral pterygoid muscle with the ipsilateral medial pterygoid muscle results in lateral movement of the mandible to the contralateral side. The bilateral contraction of the muscle, on the other hand, elevates the mandible and closes the mouth.
The superior belly was classically believed to be involved in the elevation of the mandible to close the mouth. However, recent studies suggest that it may play a more significant role in opening the mouth, along with protrusion and contralateral deviation. The inferior belly, meanwhile, was thought to depress, protrude, and deviate the mandible to the contralateral side.
The lateral pterygoid muscle is active during mastication, mandibular movements, speaking, singing, and clenching. It is the only muscle among the masticatory muscles with horizontally arranged fibres. This unique arrangement allows the muscle to exhibit a range of mediolateral and superoinferior movements.
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The orbicularis oris muscle closes or purses the lips
The human face has about 20 main facial muscles that enable essential functions like chewing and making facial expressions. One such muscle is the orbicularis oris muscle, which is responsible for closing or pursing the lips.
The orbicularis oris muscle is a circle of muscle fibres that surrounds the mouth. It is one of the muscles that control the lips, with the mentalis muscle controlling the lower lip and the levator labii superioris, levator labii superioris alaeque nasi, and zygomaticus minor muscles lifting the upper lip.
The orbicularis oris muscle is a sphincter muscle, which means it closes or tightens an opening. In this case, it closes or purses the lips. This muscle is important for functions such as speaking, eating, and making facial expressions.
The facial muscles are part of the skeletal system, also known as the musculoskeletal system. They are flat skeletal muscles that attach to different places on the skull. These muscles originate from bone or fascia and insert into the skin.
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Frequently asked questions
The muscle that closes the mouth is called the medial pterygoid. It is one of four muscles of mastication, which are a group of muscles associated with movements of the jaw.
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 and assist in grinding food.
The other three muscles of mastication are the masseter, temporalis, and lateral pterygoid.
The masseter elevates the mandible and approximates the teeth. It also functions to retract the mandible.
The temporalis muscle functions as an elevator of the mandible. It also contributes to grinding movements by moving the mandible from side to side.
