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The mandible is the largest and strongest bone in the human skull, forming the lower jaw and holding the lower teeth in place. It is the only movable bone in the skull, sharing joints with the cranium's temporal bones. The mandible is composed of a horseshoe-shaped body and a pair of rami, which project upwards to form a temporomandibular joint. The mandible is subject to various muscles, including the temporalis, masseter, medial pterygoid, and lateral pterygoid muscles, collectively known as the muscles of mastication. These muscles attach to the mandible at various points, such as the coronoid process and the rami, and enable essential functions like chewing and grinding. The mandible also houses nerves, some connecting to the teeth, and blood vessels. This complex structure plays a crucial role in facial structure and oral functions.
| Characteristics | Values |
|---|---|
| Description | The mandible is the largest and strongest bone of the face. It forms the lower jaw and holds the lower teeth in place. |
| Movability | The mandible is the only freely moving bone in the skull. |
| Shape | The body of the mandible is curved and shaped much like a horseshoe. |
| Borders | Alveolar border (superior), base (inferior) |
| Surfaces | Outer, inner |
| Bones | Two halves joined at the mandibular symphysis |
| Landmarks | Condylar process, coronoid process, mandibular notch, mandibular foramen, mental foramen, oblique line, mental protuberance, mental tubercle, sublingual fossa, mylohyoid line, condyle, gonial angle, mandibular canal, mental spine, digastric fossa, masseteric tuberosity, pterygoid tuberosity, mylohyoid sulcus |
| Muscles | Temporalis, masseter, medial pterygoid, lateral pterygoid, depressor anguli oris, platysma, genioglossus, geniohyoid, mylohyoid, superior pharyngeal constrictor, buccinator |
| Joints | Temporomandibular joint |
| Fractures | Condylar neck fracture, mandibular neck fracture, angle of mandible fracture |
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What You'll Learn
The mandible is the largest bone of the facial skeleton
The ramus is the vertical part of the mandible. The point at which it unites with the body is called the angle of mandible, or gonial angle. The angle can range from 110° to 130° and can vary depending on age, sex, and ethnicity. The superior part of the ramus consists of two processes: the coronoid process (anterior process) and the condylar process (posterior process). The incisure between them is called the mandibular notch and it is crossed by the masseteric nerve and vessels. The coronoid process features the temporal crest, which serves as an attachment point for the temporalis muscle. The condylar process has an articular surface (the condyle), via which the mandible articulates with the articular tubercle of the temporal bone to form the temporomandibular joint.
The mandible hosts the lower teeth, and many muscles, nerves, and blood vessels attach to the bone. The temporalis muscle attaches to the coronoid process, and the masseter attaches to the rami. The lateral pterygoid inserts into the neck of the mandible, and the medial pterygoid inserts into the ramus near the angle of the mandible. The mandibular canal, with the mental foramen opening from it, is closer to the alveolar border. The mental foramen acts as a passageway for neurovascular structures. The mandible is prone to fracture, especially due to trauma, and is routinely used to determine the age of the deceased.
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The mandible forms the lower jaw and holds the lower teeth in place
The mandible is the largest and strongest bone of the face. It is also the only movable bone in the skull. The mandible forms the lower jaw and holds the lower teeth in place. The body of the mandible is curved and shaped like a horseshoe. It has two borders: the alveolar border, which contains 16 sockets to hold the lower teeth, and the base, which is the site of attachment for the digastric muscle. The body is marked in the midline by the mandibular symphysis, a small ridge of bone that represents the fusion of the two halves of the mandible during development. The symphysis encloses a triangular eminence, the mental protuberance, which forms the shape of the chin.
The ramus is the vertical part of the mandible. It is a lateral continuation of the body and is quadrilateral in shape. The point at which the ramus meets the body is called the angle of mandible, or gonial angle. The superior part of the ramus consists of two processes: the coronoid process (anterior) and the condylar process (posterior). The incisure between them is called the mandibular notch. The condylar process has an articular surface (the condyle), which allows the mandible to articulate with the articular tubercle of the temporal bone to form the temporomandibular joint.
The mandible is subject to various muscles attaching to it, including the masseter, medial pterygoid, lateral pterygoid, temporalis, depressor labii inferioris, depressor anguli oris, platysma, genioglossus, geniohyoid, and mylohyoid muscles. The temporalis muscle is a large, flat muscle that lies within the temporal fossa of the skull. It functions mainly as an elevator of the mandible. The masseter muscle is a strong, quadrangular muscle that covers the lateral aspect of the ramus of the mandible. Its major function is to elevate the mandible, with a minor contribution to protrusion of the mandible. The medial pterygoid muscle is also quadrangular and is situated in the infratemporal fossa.
The mandible is of great forensic significance. As the mandible changes throughout an individual's life, it is often used to determine the age of the deceased. Mandibular fractures are most commonly caused by trauma and typically occur in two places. A fractured neck of the mandible is often observed in conjunction with a fracture of the contralateral mandibular body.
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The body of the mandible is curved and horseshoe-shaped
The mandible is the largest bone of the facial skeleton and the only movable bone of the skull. It is also known as the lower jaw and is located inferior to the maxilla. The mandible holds the lower teeth in place and has two surfaces and two borders. The body of the mandible is curved and shaped much like a horseshoe. It has two borders: an alveolar border (superior) and a base (inferior). The alveolar border contains 16 sockets to hold the lower teeth. The base is the inferior part of the body and features several anatomical landmarks.
The body of the mandible is marked in the midline by the mandibular symphysis, a small ridge of bone that represents the fusion of the two halves during development. The symphysis encloses a triangular eminence, the mental protuberance, which forms the shape of the chin. Lateral to the mental protuberance is the mental foramen, which acts as a passageway for neurovascular structures. The mental foramen is positioned on the external surface of the mandibular body, below the second premolar tooth. It allows the inferior alveolar nerve and artery to exit the mandibular canal. The mandible is composed of a horseshoe-shaped body and a pair of rami, which project upwards to form a temporomandibular joint.
The ramus is the vertical part of the mandible. The point at which it unites with the body is called the angle of mandible, or gonial angle. The angle can range from 110° to 130° and can vary depending on age, sex, and ethnicity. The superior part of the ramus consists of two processes: the coronoid process (anterior process) and the condylar process (posterior process). The incisure between them is called the mandibular notch and it is crossed by the masseteric nerve and vessels. The condylar process has an articular surface (the condyle), through which the mandible articulates with the articular tubercle of the temporal bone to form the temporomandibular joint.
The mandible is subject to fracturing and is of great forensic significance. As the mandible progressively changes over an individual's life, it is routinely used to determine the age of the deceased. Mandibular fractures are most commonly caused by trauma and typically occur in two places. The parasymphysis is especially prone to fracture due to the incisive fossa and mental foramen. Involvement of the inferior alveolar nerve in the callus may cause neuralgic pain. Other common sites for fractures are the neck and angle of the mandible.
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The mandible has two borders: the alveolar border and the base
The mandible is the largest bone of the facial skeleton and the only mobile bone of the skull. It forms the lower jaw and holds the lower teeth in place. The body of the mandible is curved and shaped like a horseshoe. It has two borders: the alveolar border (superior) and the base (inferior).
The alveolar border of the mandible is the superior border, meaning it is located on the top side of the mandible bone. This border is wider at the back than at the front and is hollowed into cavities to receive the teeth. There are 16 of these cavities, or sockets, which vary in depth and size according to the teeth they contain. The Buccinator muscle attaches to the outer lip of the alveolar border, as far forward as the first molar tooth.
The base of the mandible is the inferior border, meaning it is located on the underside of the mandible bone. This is the lower part of the mandible, excluding the alveolar part. The base features several anatomical landmarks on its external and internal surfaces. The external surface includes the mandibular symphysis, a fibrous tissue in the midline of the mandibular body that ossifies by the first year of life. The symphysis unites the left and right halves of the mandible to form a single, symmetrical bone. The mental protuberance is a triangular eminence enclosed by the symphysis, which forms the shape of the chin.
The base of the mandible also includes the mental tubercle, a paired bony prominence on each side of the mental protuberance, and the oblique line, a crest extending from the ramus to the body of the mandible. This provides the insertion point for the depressor anguli oris muscle. The mental foramen is another feature of the base of the mandible, located inferior to the second mandibular premolar tooth. It acts as a passageway for neurovascular structures, allowing the inferior alveolar nerve and artery to exit the mandibular canal.
The internal surface of the base of the mandible features the digastric fossa, a paired depression on the lower margin of the mandibular body located on each side of the midline. The base of the mandible is also the site of attachment for the digastric muscle medially.
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The mandible is the only movable bone in the skull
The mandible is the largest bone in the human skull and the only movable bone in the skull. It is commonly known as the lower jaw and is located under the maxilla. It is composed of a horseshoe-shaped body that holds the teeth, and a pair of rami that project upwards to form a temporomandibular joint. The mandible is formed by a body and a pair of rami, along with condyloid and coronoid processes. The body of the mandible has two surfaces: an outer and an inner surface, and two borders: an upper and a lower border. The outer surface is also known as the external surface and has the following characteristics: mandibular symphysis/symphysis menti at midline, which joins the left and right halves of the bone. This is detected as a subtle ridge in adults.
The mandible is a vital bone in the skull, serving several important functions. One of its primary roles is to hold and support the lower teeth. The alveolar border of the mandible contains 16 sockets to securely hold the lower teeth in place. The mandible also provides structural support for the chin. The front part of the mandible contributes to the formation of the chin, giving it shape and definition.
The mandible also plays a crucial role in chewing and speaking. Unlike other bones in the skull, the mandible articulates with the surrounding bones through a synovial joint called the temporomandibular joint. This unique joint allows the mandible to produce a wide range of movements, including opening and closing the mouth, as well as articulating the jaw side to side and forward and back. These complex movements facilitated by the mandible are essential for chewing food and speaking.
Additionally, the mandible serves as an important attachment site for several muscles. Muscles such as the temporalis, masseter, lateral pterygoid, and medial pterygoid insert into different parts of the mandible. These muscle attachments provide stability and facilitate the movement of the mandible during various facial expressions and functions, such as chewing and speaking.
The mandible is also associated with various pathological conditions. Alveolar bone resorption, for example, occurs when teeth are lost, leading to a lack of structural support for the bone. Condylar fractures are the most frequent type of mandibular fractures, usually resulting from car accidents or indirect force due to violence. Other areas susceptible to fractures include the body, angle, symphysis, ramus, alveolus, and coronoid process.
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Frequently asked questions
The mandible is the largest bone in the human skull and forms the lower jawline.
The mandible has a U-shaped body with two surfaces and two borders. The body of the mandible is curved and shaped like a horseshoe.
The temporalis, medial pterygoid, lateral pterygoid, and masseter muscles are all attached to the mandible.
The mandible holds the lower teeth in place and is the only movable bone in the skull. It is essential for chewing food.
The mandible changes throughout an individual's life and can be used to determine age. In infants and children, the angle of the mandible is more obtuse, making the head in line with the body of the mandible. In adults, the angle decreases, making the ramus almost vertical.
