Jawbone
Mandibula
location_on Lower face, forming the lower jaw
The mandible is the largest and strongest bone of the face and the only movable bone of the skull. It consists of a horseshoe-shaped body bearing the lower teeth and two vertical rami that articulate with the temporal bones at the temporomandibular joints. The mandible transmits the forces of mastication and is the last skull bone to complete ossification.
Key Anatomical Features
- Mental foramen transmits the mental nerve providing sensation to the chin and lower lip
- Mandibular foramen on the medial ramus surface is the target for inferior alveolar nerve blocks
- Coronoid process provides attachment for the temporalis muscle
- Condylar process (head) articulates with the temporal bone at the TMJ
- Alveolar process contains sockets (alveoli) for the 16 lower teeth
- Angle of the mandible is where the body meets the ramus, approximately 120 degrees in adults
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| Masseter | Lateral surface of ramus and angle | Elevates the mandible (closes mouth), most powerful jaw closer |
| Temporalis | Coronoid process and anterior ramus | Elevates and retracts the mandible |
| Medial pterygoid | Medial surface of angle and ramus | Elevates the mandible |
| Lateral pterygoid | Neck of condylar process (pterygoid fovea) | Protrudes the mandible and opens the mouth |
| Digastric (anterior belly) | Digastric fossa on inferior body | Depresses the mandible |
| Mylohyoid | Mylohyoid line on inner body | Elevates the floor of the mouth and hyoid |
| Genioglossus | Superior genial tubercle | Protrudes and depresses the tongue |
| Geniohyoid | Inferior genial tubercle | Elevates the hyoid and depresses the mandible |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Temporomandibular joint (left) | Synovial modified hinge with articular disc | Temporal bone |
| Temporomandibular joint (right) | Synovial modified hinge with articular disc | Temporal bone |
| Mandibular symphysis | Fused fibrous (in adults) | Opposite mandibular half |
Common Pathologies
Mandibular fracture
The third most common facial fracture, frequently occurring at the condylar neck, angle, and parasymphysis. Often presents as bilateral fractures because the mandible is a ring-like structure.
TMJ dysfunction
Disc displacement, osteoarthritis, or myofascial pain affecting the jaw joint causing pain, clicking, locking, and limited opening.
Osteonecrosis of the jaw
Bone death in the mandible associated with bisphosphonate therapy, radiation therapy, or antiangiogenic medications. More common in the mandible than maxilla due to its relatively limited blood supply.
Mandibular torus
Benign bony growth on the lingual surface of the mandible near the premolars, present in up to 10% of the population.
Clinical Relevance
The mandible is commonly fractured at its weakest points: the condylar neck, angle (especially when a third molar is present), and parasymphysis. The inferior alveolar nerve runs through the mandibular canal and can be damaged during fractures, extractions, or dental implant placement. Ludwig angina, a floor-of-mouth infection that can spread along fascial planes from mandibular dental infections, is a life-threatening emergency due to airway compromise.
Development and Ossification
The mandible develops from intramembranous ossification in Meckel's cartilage of the first pharyngeal arch, beginning around the 6th fetal week. It is initially two separate halves that fuse at the mandibular symphysis during the first year of life. The mandible continues to grow and remodel significantly into the late teens.
Did You Know?
- The mandible is the first bone to begin ossification in the skull, starting around the 6th fetal week
- The angle of the mandible changes throughout life: about 140 degrees at birth, 120 degrees in adults, and back to 140 degrees in edentulous elderly
- The bite force generated through the mandible can exceed 70 kilograms in the molar region
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