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Mandible

The mandible is the largest bone of the fascial skeleton (viscerocranium). Besides the bones of the middle ear, the mandible is the only mobile bone in the skull. Unlike other bones of the skull, the mandible doesn’t articulate with the surrounding bones via sutures, but rather via a synovial joint called the temporomandibular joint. This joint allows the mandible to be attached to the skull while at the same time being capable of producing various translatory and rotatory movements. These movements allow complex actions like chewing and speaking.

The mandible consists of two main parts: a body and two rami. These parts feature various anatomical landmarks participate in important functions of the mandible, for example housing the teeth and providing the passage for neurovascular structures.

This article will discuss the anatomy of the mandible.

Key facts about the mandible
Definition A horseshoe-shaped mobile bone of the viscerocranium that forms the lower jaw and houses the mandibular teeth
Main parts Body of mandible, ramus of mandible
Bony landmarks of the body Mental protuberance, mental tubercle, mental foramen, oblique line of mandible, sublingual fossa, mylohyoid line, submandibular fossa, mental spines, digastric fossa, alveolar part, interalveolar septa
Bony landmarks of the ramus Coronoid process, mandibular notch, condylar process, head of mandible, neck of mandible, pterygoid fovea, pterygoid tuberosity, masseteric tuberosity, angle of mandible, mandibular foramen, lingula, mylohyoid groove
Contents
  1. Anatomy
    1. Body
    2. Ramus
  2. Muscles that attach to the mandible
  3. Clinical relations
  4. Sources
+ Show all

Anatomy

The mandible is a horseshoe shaped bone of the viscerocranium. It consists of the body and two rami, connected at the angle of mandible.

Body

The body of mandible is its horizontal portion. It consists of two parts: 

  • The alveolar part
  • The base of mandible

The alveolar part is the upper portion of the body. It consists of two bony lamellae: a thick buccal lamella, and a thin lingual lamella. They are parallel to each other, forming a shallow trench on the upper surface of the alveolar part. The lamellae are connected by interalveolar septa, which cut the trench into sockets which house the mandibular teeth. 

The base is the inferior part of the body that features several anatomical landmarks. On its external surface, we can identify:

  • The mandibular symphysis: Fibrous tissue in the midline of the mandibular body, which ossifies by the first year of life. It unites the left and right halves of the mandible in order to form a single, symmetrical bone. 
  • The mental protuberance: A bony prominence at the midline of the body.
  • The mental tubercle: A paired bony prominence on each side of the mental protuberance.
  • The oblique line: A crest extending from the ramus to the body of mandible. It provides the insertion point for the depressor anguli oris muscle.

The mental foramen: An opening located inferior to the second mandibular premolar tooth which provides the passage for the mental nerve and vessels.

Try out our free labeling diagrams about the bones of the skull to enhance your learning

The internal surface of the base of mandible features the following landmarks:

  • The digastric fossa: A paired depression on the lower margin of the mandibular body, located on each side of the midline.
  • The superior and inferior mental spines: Paired bony eminences on the midline of the internal surface of the body. They provide the attaching point for the genioglossus and geniohyoid muscles.
  • The submandibular fossa: A paired depression on each side of the mental spines which houses the submandibular gland.
  • The sublingual fossa: A depression located superior to the mental spines which hosts the sublingual gland.
  • The mylohyoid line: A paired oblique crest on the sides of the body to which the mylohyoid muscle attaches.

Ramus

The ramus is the vertical part of the mandible. The point at which it unites with the body is called the angle of mandible (i.e. gonial angle). The angle can range from 110° to 130° and can vary depending on the age, sex and etnicity. Usually, the angulation is larger in men.

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. 

On the posterolateral aspect of the ramus there is a single landmark called the masseteric tuberosity, a rough surface that serves for the insertion of the masseter muscle

The medial surface of the rami harbours following landmarks:

  • The pterygoid tuberosity: A rough area for the insertion of the medial pterygoid muscle.
  • The mandibular foramen: The starting point of the mandibular canal which is traversed by the inferior alveolar nerve and its branches.
  • The mylohyoid sulcus: A small sulcus which contains the mylohyoid artery and nerve.

Muscles that attach to the mandible

Besides the sphenomandibular and stylomandibular ligaments, and the pterygomandibular raphe, there are numerous muscles that attach to the mandible.

They are presented in the tables below:

Muscles that originate from the mandible
Buccinator muscle Buccinator ridge of mandible
Mentalis muscle Incisive fossa of mandible
Depressor labii inferioris muscle Oblique line of mandible
Depressor anguli oris muscle Mental tubercle and oblique line of mandible
Anterior belly of digastric muscle Digastric fossa
Genioglossus muscle Superior mental spine
Geniohyoid muscle Inferior mental spine
Mylohyoid muscle Mylohyoid line
Muscles that insert to the mandible
Lateral pterygoid muscle Pterygoid fossa
Temporalis muscle Apex and medial surface of coronoid process of mandible
Medial pterygoid muscle Medial surface of ramus (pterygoid tuberosity) and angle of mandible
Masseter muscle Lateral surface of ramus and angle of mandible
Platysma Lateral surface of ramus and angle of mandible

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