Learning Objective: Understand the anatomy of the mandible—its parts, foramina, muscular attachments, articulations, and clinical relevance—particularly in relation to fractures and the temporomandibular joint (TMJ).
The mandible is the largest and strongest bone of the face, forming the lower jaw and housing the lower teeth.
It articulates bilaterally with the temporal bones at the temporomandibular joints (TMJs), which are essential for mastication and speech.
Etymology: The word mandible originates from the Latin mandibula, meaning “jawbone.”
Anatomical Structure
The mandible has two main components:
- Body – horizontal portion forming the chin and bearing the lower teeth.
- Rami – vertical extensions projecting upward from the posterior body.
These meet at the angle of the mandible on each side.
Body of the Mandible
The body is curved and roughly horseshoe-shaped. It has two borders and notable surface features:
- Alveolar border (superior):
Contains 16 sockets (alveoli) for the lower teeth. - Base (inferior):
Provides attachment to the digastric muscle medially. - Midline:
The mandibular symphysis marks the fusion line of the two halves during development, enclosing a triangular mental protuberance that forms the chin. - Mental foramen:
Located below the second premolar tooth on each side, transmitting the mental nerve and vessels to supply the chin and lower lip.
Rami of the Mandible
Each ramus is quadrilateral and projects superiorly from the body.
It bears several important landmarks:
- Head (condylar process):
Articulates with the mandibular fossa of the temporal bone to form the TMJ. - Neck:
Below the head, it serves as an attachment for the lateral pterygoid muscle. - Coronoid process:
Sharp anterior projection providing attachment to the temporalis muscle. - Mandibular foramen (medial surface):
Entry for the inferior alveolar nerve and artery into the mandibular canal, which runs through the bone and exits at the mental foramen.
Foramina and Canals
| Foramen | Location | Structures Passing Through |
|---|---|---|
| Mandibular foramen | Medial surface of ramus | Inferior alveolar nerve & artery |
| Mental foramen | Below the 2nd premolar on the external surface | Mental nerve & vessels (continuation of inferior alveolar) |
Muscular Attachments
| Region | Muscles Attached | Function / Action |
|---|---|---|
| External surface of the body | Mentalis, Buccinator, Platysma, Depressor labii inferioris, Depressor anguli oris | Facial expression, lip movement |
| Internal surface of the body | Genioglossus, Geniohyoid, Mylohyoid, Digastric (anterior belly) | Tongue & floor of mouth support |
| Ramus and processes | Masseter, Temporalis, Medial & Lateral pterygoids | Mastication |
The temporalis attaches to the coronoid process, while the masseter and medial pterygoid strengthen the mandible laterally and medially.
Articulations
The mandible articulates with the temporal bone at the temporomandibular joint (TMJ) — a synovial joint that allows both hinge and gliding movements.
Clinical Relevance
- Mandibular Fractures: Fractures of the mandible often occur bilaterally or at two sites, due to the ring-like shape of the bone.
- Common fracture patterns:
- Coronoid process: Rare, usually solitary.
- Neck of mandible: Transverse fractures; may dislocate TMJ.
- Angle of mandible: Often oblique, may involve the third molar socket.
- Body of mandible: Commonly passes through the canine tooth.
- Common fracture patterns:
🩻 Clinical note: Always assess the contralateral side for an associated fracture.
Mandibular Nerve Block
Local anesthesia targeting the inferior alveolar nerve is administered near the mandibular foramen.
It numbs the ipsilateral lower teeth, chin, and lower lip.
Temporomandibular Joint Dysfunction
Injury or muscle imbalance can cause TMJ pain, clicking, and limited movement.
The lateral pterygoid and temporalis play key roles in joint stability.
Key Points
- The mandible forms the lower jaw and supports the lower teeth.
- It articulates with the temporal bone at the TMJ.
- Two major foramina transmit the inferior alveolar and mental nerves.
- Fractures are often bilateral; always check the contralateral side.
