The mandible is the single midline bone of the lower jaw. It consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami, which unite with the ends of the body nearly at right angles (angle of the jaw). It articulates with both temporal bones at the mandibular fossa at the temporomandibular joints (TMJ). It bears the lower tooth-bearing alveolar process.
Gross anatomy
Osteology
Body
The body of the mandible is curved, somewhat like a horseshoe, with two surfaces and two borders. The mandibular symphysis is located in the midline, a point of fusion. The parasymphysis extends from the midline to past the canine.
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external surface
midline ridge indicating the symphysis
mental foramen: inferior to the second premolar tooth (with normal variants between the canine and 1st molar), midway between the superior and inferior borders; allows for the passage of the mental vessels and mental nerve
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internal surface
concave from side-to-side
origin of geniohyoid and genioglossus (from mental spines) and mylohyoid (mylohyoid line)
fossae for the sublingual and submandibular salivary glands
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superior (or alveolar) border
wider behind than in front
hollowed for reception of teeth (normally 16)
attachment of buccinator muscle
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inferior border
rounded, longer than the superior border and thicker in front than behind
groove for the facial artery may be present at the point it joins the ramus of the mandible
Ramus
The ramus is quadrilateral in shape, and has two surfaces, four borders, two processes and one canal:
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external (or lateral) surface
flat; gives attachment to the masseter muscle
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inner (or medial) surface
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mandibular foramen: opening of the mandibular canal, which transmits the inferior alveolar vessels and nerve
lingula of the mandible: prominent, sharp ridge in front of the mandibular foramen; gives attachment to the sphenomandibular ligament
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lower border
thick, straight and continuous with the inferior border of the body of the mandible
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posterior border
thick, smooth, rounded and covered by the parotid gland
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angle of the mandible is at its junction of the posterior border and the body
medial pterygoid muscle inserts into the medial aspect of the angle of the mandible
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anterior border
thin above and thicker below; continuous with the oblique line
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upper border
thin
consists of the coronoid process anteriorly and the condylar process posteriorly separated by the mandibular notch (a.k.a. sigmoid notch)
The mandibular canal runs obliquely downward and forward in the ramus, and then horizontally forward in the body, where it is placed under the alveoli and communicates with them by small openings. On arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off two small canals which run to the cavities containing the incisor teeth. It contains the inferior alveolar vessels and nerves, from which branches are distributed to the teeth via the incisive nerve.
Coronoid process
thin, triangular eminence from the upper border of the ramus of the mandible
separated from the condylar process posteriorly by the mandibular notch
temporalis muscle inserts into its medial and lateral surfaces
masseter muscle also inserts into its lateral surface
Condylar process
The condylar process includes the rounded articular condyle (contributing to the TMJ) and the condylar neck. Please refer to our article on the condylar process of the mandible for a specific discussion.
Arterial supply
facial artery (branch of external carotid artery)
lingual artery (branch of the external carotid artery)
inferior alveolar artery (branch of the maxillary artery)
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