Mandible

Overview

The bone of the lower jaw, consists of a horseshoe shaped body, and two rami attached to the
posterior ends of the body almost at 90 degrees, forming the angle of the mandible

Structure

Body

Horse-shoe shaped anterior portion of the mandible, bound by two surfaces and two borders.

• External surface: Contains the mandibular symphysis, a subtle midline ridge which divides inferiorly to enclose a triangular depression called the mental protuberance. The elevated edges of the mental protuberance form the mental tubercle. Lateral to the ridge and inferior to the incisive teeth is the incisive fossa.
• Internal surface: Contains the median ridge and mental spines laterally.
• Alveolar (superior) border: Contains the hollow cavities which house the lower sixteen teeth.
• Inferior border: Creates the low jawline and site of attachment for the diagastric muscle medially.

Rami

Contributes to the lateral portion of the mandible, projecting cranially from the mandibular (gonial) angle.

• Head: posterior articulates with the temporal bone to form the temporomandibular joint

• Neck: supports the head. Site of lateral pterygoid muscle.

• Coronoid process

Muscular Attachments

Muscles Originating from the Mandible

• Mentalis – originates from the incisive fossa
• Orbicularis oris – originates from the incisive fossa
• Depressor labii inferioris – originates from the oblique line
• Depressor anguli oris – originates from the oblique line
• Buccinator – originates from the alveolar process
• Digastric anterior belly – originates from the digastric fossa
• Mylohyoid – originates from the mylohyoid line
• Geniohyoid – originates from the inferior portion of the mental spine
• Genioglossus – originates from the superior portion of the mental spine
• Superior pharyngeal constrictor – originates partially from the pterygomandibular raphe, which originates from the mylohyoid line

Muscles Inserting on the Mandible

• Platysma – inserts on the inferior border of the mandible
• Superficial masseter – inserts on the lateral surface of the ramus and angle of the mandible
• Deep masseter – inserts on the lateral surface of the ramus and angle of the mandibleMedial pterygoid – inserts on the medial surface of the mandibular angle and ramus of the mandible
• Inferior head of the lateral pterygoid – inserts on the condyloid process
• Temporalis – inserts on the coronoid process

Mandibular canal
– Lingula
– Inferior alveolar foramen
– Mental foramen

The inferior alveolar artery is a branch of the 1st part of the maxillary artery.

Course

• Descends through the infratemporal fossa with the inferior alveolar nerve to enter the mandibular foramen on the medial surface of the ramus of the mandible.
• Runs with inferior alveolar nerve along the mandibular canal and bifurcates into incisive and mental branches, opposite the first pre-molar tooth.
• Incisive branch: continues towards the midline where it anastomoses with the opposite artery.
• Mental branch: exits the mandible at the mental foramen. Anastomeses with the submental and inferior labial arteries.

Supplies

• Mandibular teeth.
• Incisive branch: root and pulp of mandibular teeth.
• Mental branch: chin.

The inferior alveolar artery is a branch of the 1st part of the maxillary artery.

Course

• Descends through the infratemporal fossa with the inferior alveolar nerve to enter the mandibular foramen on the medial surface of the ramus of the mandible.
• Runs with inferior alveolar nerve along the mandibular canal and bifurcates into incisive and mental branches, opposite the first pre-molar tooth.
• Incisive branch: continues towards the midline where it anastomoses with the opposite artery.
• Mental branch: exits the mandible at the mental foramen. Anastomeses with the submental and inferior labial arteries.
•  

Supplies

• Mandibular teeth.
• Incisive branch: root and pulp of mandibular teeth.
• Mental branch: chin.