Logan Steele
The mandible is the largest bone in the human skull, forming the lower jawline and shaping the contour of the inferior third of the face. It serves as the attachment point for various muscles, including the muscles of mastication, which are responsible for chewing food. These muscles include the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. The mandible is also the insertion point for muscles involved in facial expressions and tongue movements. The specific muscles connected to the mandible vary depending on its external, internal, and lateral surfaces, as well as its rami and coronoid process.
| Characteristics | Values |
|---|---|
| Shape | U-shaped or horseshoe-shaped |
| Position | Forms the lower jawline and shapes the contour of the inferior third of the face |
| Bone Type | Largest and strongest bone of the face |
| Muscle Attachment Sites | External (lateral) surface: mentalis, buccinator, platysma, depressor labii inferioris, depressor anguli oris. Internal (medial) surface: genioglossus, geniohyoid, mylohyoid and digastric. Mandibular rami: masseter, temporalis, medial pterygoid and lateral pterygoid |
| Muscle Functions | Elevation, depression, protrusion, retraction, side-to-side movement, grinding of food, approximation of teeth |
| Muscle Innervation | Mandibular division of the trigeminal nerve (CNV3) |
| Muscle Blood Supply | Branches of the maxillary artery |
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What You'll Learn
The temporalis muscle attaches to the coronoid process
The mandible is the largest bone in the human skull, forming the lower jawline and shaping the contour of the inferior third of the face. It is also the strongest bone of the face and the only mobile bone of the skull. The mandible serves as the attachment point for various muscles, including the temporalis muscle.
The temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic arch. In humans, the temporalis muscle arises from the temporal fossa and the deep part of the temporal fascia. This is a very broad area of attachment. It passes medial to the zygomatic arch. It forms a tendon that inserts onto the coronoid process of the mandible.
The coronoid process is located at the superior aspect of the ramus. Its anterior border is continuous with that of the ramus, and its posterior border creates the anterior boundary of the mandibular notch. The temporalis muscle and masseter insert on its lateral surface. The coronoid process features the temporal crest, which serves as an attachment point for the temporalis muscle.
The temporalis muscle can be divided into two functional parts: the anterior and posterior. The anterior portion runs vertically, and its contraction results in the elevation of the mandible (closing the mouth). The posterior portion has fibres that run horizontally, and contraction of this portion results in the retrusion of the mandible. The middle portion, where fibres run in an oblique direction towards the inferior and anterior, is used for both elevation and retraction of the mandible. In a unilateral contraction, it provokes lateral movement of the mandible.
The temporalis muscle is the strongest muscle of the temporomandibular joint and the primary retractor of the mandible. The contraction of the posterior fibres of the temporalis muscle results in the backward movement of the mandible (retrusion). The contraction of its anterior fibres moves the mandible dorsocranially (elevation). In unison, these actions facilitate the closing of the mouth and the approximation of the teeth.
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The masseter muscle attaches to the rami
The masseter muscle is one of the four muscles of the masticatory apparatus, along with the temporalis, medial pterygoid, and lateral pterygoid. It is the most powerful muscle of mastication, responsible for elevating the mandible and causing a powerful jaw closure. The masseter muscle attaches to the rami of the mandible, with its superficial part originating from the maxillary process of the zygomatic bone and running inferoposteriorly to the masseteric tuberosity on the ramus. The deep part of the masseter muscle consists of vertically directed muscle fibres that originate from the inferior border of the zygomatic arch and insert onto the superficial side of the ramus of the mandible.
The mandible is the largest bone in the human skull, forming the lower jawline and shaping the contour of the inferior third of the face. It is also the only mobile bone of the skull. The ramus is the vertical part of the mandible, with the superior part consisting of two processes: the coronoid process (anterior) and the condylar process (posterior). The masseteric nerve and vessels cross the incisure between these two processes, known as the mandibular notch. The masseter muscle attaches to the ramus of the mandible at the masseteric tuberosity, a rough surface on the posterolateral aspect of the ramus.
The masseter muscle has two parts: a deep part and a superficial part. The deep part is smaller and more muscular in texture, originating from the posterior third of the lower border and the medial surface of the zygomatic arch. Its fibres pass downward and forward, inserting into the upper half of the ramus near the coronoid process. The superficial part of the masseter muscle is larger and arises from the anterior two-thirds of the inferior border of the zygomatic arch. Its fibres pass inferior and posterior, inserting into the angle of the mandible and the inferior half of the lateral surface of the ramus.
The masseter muscle is innervated by the anterior division of the mandibular division (V3) of the trigeminal nerve. It is supplied with blood by the masseteric artery, a branch of the maxillary artery. The masseter muscle can become enlarged in individuals who habitually clench or grind their teeth or chew gum, a condition known as masseteric hypertrophy. This enlargement is usually asymptomatic and soft, and it can be unilateral or bilateral.
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The lateral pterygoid inserts into the neck of the mandible
The mandible is the largest bone in the human skull, forming the lower jaw and shaping the contour of the inferior third of the face. It is also the strongest bone of the face and the only mobile bone in the skull. The mandible serves as the attachment point for various muscles, including the muscles of mastication.
The lateral pterygoid is one of the four muscles of mastication, along with the medial pterygoid, temporalis, and masseter muscles. The lateral pterygoid muscle is a craniomandibular muscle that plays a crucial role in the inferior temporal region. It is active during mastication and mandibular movements, including protrusion (forward movement of the mandible), abduction (depression of the mandible), and mediotrusion (mandibular condyle movement towards the midline). The lateral pterygoid muscle has two heads or bellies, with the inferior belly being three times larger than the superior belly. The lateral pterygoid is unique among the masticatory muscles in that it is the only one with horizontally arranged fibres.
The mandible is the insertion point for a range of muscles involved in facial expression. Mandible fractures are relatively common, particularly among young males, and half of these fractures are caused by interpersonal violence. The mandible is curved and shaped like a horseshoe, with two borders: the alveolar border (superior) and the base (inferior). The body of the mandible is marked in the midline by the mandibular symphysis, which is a small ridge of bone that represents the fusion of the two halves during development.
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The medial pterygoid inserts into the ramus
The mandible, or jawbone, is the largest bone in the human skull, forming the lower jawline and shaping the lower third of the face. It is also the only mobile bone in the skull. The mandible serves as the attachment point for a range of muscles, including the medial pterygoid muscle.
The medial pterygoid muscle is a thick, quadrilateral-shaped masticatory muscle located on the medial aspect of the lower jaw bilaterally. It is also referred to as the internal pterygoid muscle. This muscle is responsible for several functions, including elevating the mandible (closing the mouth), protruding the mandible, mastication (chewing), and excursing the mandible.
The medial pterygoid muscle consists of two heads: a deep head and a superficial head. The deep head is larger and arises from the medial surface of the lateral pterygoid plate of the sphenoid bone, while the superficial head is smaller and originates from the maxillary tuberosity and the pyramidal process of the palatine bone. The fibres of both heads descend posterolaterally and insert into the ramus of the mandible.
The insertion of the medial pterygoid muscle occurs via a strong tendinous lamina into the triangular impression found on the medial surface of the ramus and angle of the mandible. The ramus is the vertical part of the mandible, and the angle of the mandible, or gonial angle, is the point at which the ramus unites with the body of the mandible. The fibres of the medial pterygoid muscle attach superiorly to the mandibular foramen, which is located on the internal surface of the ramus. The mandibular foramen serves as a passageway for neurovascular structures, including the inferior alveolar nerve and artery.
In summary, the medial pterygoid muscle inserts into the ramus of the mandible, contributing to the muscle's role in jaw movement and mastication. The insertion of this muscle is a complex process involving the attachment of its fibres to the medial surface of the ramus and the utilisation of a tendinous lamina to facilitate movement and function.
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The digastric muscle attaches to the internal surface of the mandible
The mandible is the largest bone in the human skull, forming the lower jawline and shaping the lower third of the face. It is also the only mobile bone in the skull. The mandible serves as the attachment point for various muscles, including the muscles of mastication, which are responsible for the chewing movement of the mandible at the temporomandibular joint.
The digastric muscle is one of the muscles that attach to the mandible. Specifically, the anterior belly of the digastric muscle attaches to the internal surface of the mandible at the digastric fossa, which is a paired depression on the lower margin of the mandibular body, located on each side of the midline. The digastric fossa is situated at the base of the mandible near the midline. The digastric muscle is a bilaterally paired suprahyoid muscle located under the jaw, and it gets its name from the fact that it has two 'bellies' or muscular bellies united by an intermediate tendon. The posterior belly of the digastric muscle is attached to the mastoid notch of the temporal bone, while the anterior belly attaches to the mandible.
The digastric muscle is involved in complex jaw actions such as speaking, swallowing, chewing, and breathing. When the hyoid bone is fixed, the digastric muscle elevates the hyoid bone and the larynx, resulting in the lowering or closing of the epiglottis, which prevents the inhalation of food or liquid during swallowing. Conversely, when the mandible is fixed, the digastric muscle depresses it, aiding in opening the mouth.
The digastric muscle also has clinical significance in pathological conditions of the mandible. For example, mandible fractures are relatively common in trauma, especially among young males, and can be caused by interpersonal violence. Additionally, alveolar bone resorption can occur when teeth are lost, leading to a lack of structures to support the bone and increased pressure due to chronic denture wearing.
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Frequently asked questions
The four main muscles that connect to the mandible are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles.
These muscles are responsible for the movement of the jaw, including elevation, depression, protrusion, retraction, and side-to-side movement. They also assist in grinding food and approximating the teeth.
The mandible is the largest and strongest bone of the face, forming the lower jaw and holding the lower teeth in place. It is also the insertion point for muscles involved in facial expression.
