Dominic Stone
The mandible is the only bone that moves during mastication, and other activities such as talking. The muscles of mastication are a group of muscles responsible for the chewing movement of the mandible at the temporomandibular joint (TMJ). These muscles enhance the process of eating and assist in grinding food. The four main muscles of mastication are the masseter, temporalis, medial pterygoid, and lateral pterygoid. The lateral pterygoid muscle is the sole muscle of mastication that causes depression of the mandible.
| Characteristics | Values |
|---|---|
| Muscles that depress the mandible | Anterior digastric, mylohyoid, and inferior head of the lateral pterygoid |
| Muscles that elevate the mandible | Masseter, temporalis, medial pterygoid, and superior head of the lateral pterygoid |
| Muscles of mastication | Masseter, temporalis, medial pterygoid, and lateral pterygoid |
| Lateral pterygoid muscle function | Depends on the degree of its contraction; bilateral contraction depresses the mandible, unilateral contraction moves the mandible to the opposite side |
| Suprahyoid muscle group | Digastric muscle, mylohyoid muscle, and geniohyoid muscle |
| Function of the medial pterygoid muscle | Assists with elevation and protrusion of the mandible; assists the lateral pterygoid muscle with side-to-side mandibular motion to help with the grinding of food |
| Function of the temporalis muscle | Elevator of the mandible; contraction of the posterior, more horizontal fibres produces a retraction of the mandible, pulling the jaw backwards |
| Function of the masseter muscle | Elevates the mandible, approximates the teeth; intermediate and deep muscle fibres retract the mandible, and the superficial fibres protrude the mandible |
Explore related products
What You'll Learn
The lateral pterygoid muscle
Unilateral contraction of the lateral pterygoid muscle, in conjunction with the ipsilateral medial pterygoid muscle, moves the mandible to the opposite side, enabling side-to-side movement during chewing. The lateral pterygoid muscle is also active during speaking, singing, and clenching, and it plays a role in controlling the function of the jaw and temporomandibular joint.
Unraveling Muscle Tension: Identifying the Root Cause
You may want to see also
Explore related products
The medial pterygoid muscle
The functions of the medial pterygoid muscle include elevating the mandible (closing the mouth), protruding the mandible, mastication (especially when the maxillary and mandibular teeth are close together), and excursing the mandible. Unilateral contraction of the medial pterygoid muscle causes a slight medial rotation of the mandible. When this occurs simultaneously with the contraction of the ipsilateral lateral pterygoid muscle, it results in a noticeable movement where the same-sided part of the mandible swings anteriorly and medially. Bilateral contraction of the medial pterygoid muscle, on the other hand, elevates and protrudes the mandible.
Smooth Muscle Mystery: Circular Muscle's Unique Composition
You may want to see also
Explore related products
The temporalis muscle
The anterior portion of the temporalis muscle moves the mandible dorsocranially (elevation), while the posterior fibres pull the mandible backward (retrusion). Contraction of the posterior fibres of the muscle results in the backward movement of the mandible, while the contraction of the anterior fibres moves the mandible upward. In unison, these actions facilitate the closing of the mouth and the approximation of the teeth. The unilateral contraction of the temporalis muscle also plays an important role in the side-to-side movements of the jaw.
Bruising and Torn Muscles: What Does It Mean?
You may want to see also
Explore related products
![McKesson Tongue Depressors [500 Count] Adult Size, Non-Sterile, Wood, Unflavored, Splinter-Free, 6 in – Use for Medical, Arts, Crafts, Spa](https://m.media-amazon.com/images/I/71PTAw2sgvL._AC_UY218_.jpg)
The suprahyoid muscle group
The stylohyoid muscles are long and thin, and they work to elevate and retract the hyoid bone, resulting in the retraction and lengthening of the floor of the mouth. Additionally, the stylohyoid helps to keep the pharynx open during inspiration by tensing the floor of the mouth. The mylohyoid muscles also elevate the hyoid bone and tense the floor of the mouth.
The geniohyoid muscles are located on either side of the midline of the neck, deep to the mylohyoid muscle. They originate from the inferior mental spine of the mandible and attach to the hyoid bone. The geniohyoid muscles work to depress the mandible and elevate the hyoid bone, pulling it anterosuperiorly, which shortens the floor of the mouth and widens the pharynx during swallowing.
All the suprahyoid muscles contribute to the floor of the mouth, but it is the mylohyoid muscles that form the muscle plate that bridges between the two rami of the mandible, also known as the oral diaphragm. This oral diaphragm separates the sublingual and submandibular regions, with the only link between them being the connective tissue on the posterior part of the mylohyoid muscles. The suprahyoid muscles, in conjunction with the infrahyoid muscles, are responsible for positioning the hyoid bone and coordinating the movements of the floor of the mouth during swallowing or vocalization.
Light Weights: Muscle Toning Myth or Method?
You may want to see also
Explore related products
![GUSTO [200 Count] 4.5 Inch Wooden Multi-Purpose Popsicle Sticks for Crafts, Ice, Ice Cream, Waxing, and Tongue Depressor Wood Sticks (Formerly Comfy Package)](https://m.media-amazon.com/images/I/81J4Abu+i1L._AC_UY218_.jpg)
The masseter muscle
The word "masseter" originates from the Greek word "μασᾶσθαι" ("masasthai"), which translates to "to chew." The masseter muscle's positioning is a distinguishing feature of hystricognathous creatures, such as mole-rats, where it passes partially through the infraorbital foramen and connects to the bone on the opposite side. In toothed whales, the masseter muscle has become redundant due to a shift from chewing to swallowing, and it now provides tissue for acoustic fat bodies used for echolocation.
Goku's Muscles: Fantasy or Achievable Goal?
You may want to see also
Frequently asked questions
The lateral pterygoid muscle is the sole muscle that causes depression of the mandible.
The function of the lateral pterygoid muscle depends on the degree of its contraction. Bilateral contraction of the lateral pterygoid muscles depresses the mandible. A unilateral contraction on a particular side moves the mandible to the opposite side, allowing for side-to-side movement during chewing.
The muscles of mastication are a group of muscles responsible for the chewing movement of the mandible at the temporomandibular (TMJ) joint. The four muscles of mastication are the masseter, temporalis, medial pterygoid, and lateral pterygoid.
The muscles of mastication enhance the process of eating and assist in grinding food. They also function to approximate the teeth. The movements performed by these muscles include elevation, depression, protrusion, retraction, and side-to-side movement.
