Mandible: bone anatomy, body, ramus and angle
- Nerve
- Highlighted area
Quick facts
- Type
- A single, unpaired, movable bone of the skull, horseshoe-shaped; it holds the lower teeth.
- Parts
- Body, two rami, angle, condylar and coronoid processes, symphysis and mental protuberance.
- Joint
- With the temporal bone, through the temporomandibular joint (TMJ), on both sides.
- Nerves
- Inferior alveolar nerve in the mandibular canal, exiting as the mental nerve; the marginal mandibular branch of the facial nerve runs near the border.
- Relevance in HOF
- Foundation of the jawline, the angle and the chin; its resorption with age changes the lower third.
- In Harmy
- Corresponds to the Jawline and Chin points of the marking.
The mandible is the bone of the lower face: single, horseshoe-shaped, and the only movable bone of the skull. It holds the lower teeth, connects to the temporal bone through the temporomandibular joint (TMJ) and serves as an anchor for the chewing muscles and part of the facial expression muscles. In HOF, it is the foundation of the lower third contour: it defines the jawline, the mandibular angle and chin projection.
What are the parts of the mandible?
| Part | Where it is | What attaches or passes there |
|---|---|---|
| Body | Horizontal, U-shaped portion with the teeth | Muscles of the lower lip and chin; mental foramen |
| Symphysis and mental protuberance | Midline, at the front | Base of the chin; mentalis muscle |
| Ramus | Vertical portion, on each side | Masseter on the outside; medial pterygoid on the inside; mandibular foramen |
| Angle (gonion) | Where the body meets the ramus | Insertions of the masseter and the medial pterygoid |
| Condylar process | Top and back of the ramus | Articulates with the temporal bone at the TMJ; lateral pterygoid at the neck |
| Coronoid process | Top and front of the ramus | Insertion of the temporalis muscle |
| Mandibular notch | Between the condyle and the coronoid | Passage of vessels and nerve to the masseter |
On the inner surface, the mandible also receives muscles of the floor of the mouth and neck, such as the mylohyoid and the anterior belly of the digastric. The platysma and the depressors of the mouth corner and lower lip attach to the lower border and the outer surface of the body.
Which nerves and vessels matter?
- Inferior alveolar nerve: a branch of the mandibular nerve (third division of the trigeminal). It enters through the mandibular foramen, on the inner surface of the ramus, runs through the mandibular canal and gives sensation to the lower teeth.
- Mental nerve: a continuation of the inferior alveolar nerve, exits through the mental foramen, usually at the level of the premolars, and gives sensation to the lower lip and chin.
- Marginal mandibular branch: the motor branch of the facial nerve that runs near the lower border of the bone and moves the lower lip. It does not run inside the bone.
- Facial artery: crosses the border of the mandible just in front of the masseter, together with the facial vein.
Mandible and maxilla: what is the difference?
The mandible is the lower bone, single and movable. The maxilla is the upper bone, made of two halves joined at the midline, fixed to the skull, which holds the upper teeth and forms part of the orbit, nose and palate. In everyday Portuguese, the word for jaw is used for both, and "lower jaw" is an old name for the mandible.
What changes with age?
With aging, and especially with tooth loss, the mandible undergoes bone resorption: the height of the body decreases, the contour loses definition and the support for soft tissues decreases. Together with the descent of tissues, this contributes to the jowl and to loss of contour. A small or recessed mandible from a young age, as in retrogenia, changes the profile and is a matter for orthodontic and surgical assessment as well as aesthetics. Hypertrophied muscles, such as the masseter in bruxism, widen the lower third.
Also called: lower jaw (old name), mandibular bone, mandibula (Latin).
Frequently asked questions
What is the difference between the mandible and the maxilla?
The mandible is the lower bone, single and movable, that holds the lower teeth and connects to the skull through the TMJ. The maxilla is the upper bone, made of two halves joined together, fixed to the skull, that holds the upper teeth. In everyday Portuguese, the word for jaw is sometimes used for both.
Which nerves pass through the mandible?
Inside the bone runs the inferior alveolar nerve, which gives sensation to the lower teeth and exits through the mental foramen as the mental nerve, responsible for sensation in the lower lip and chin. On the outside, near the border, runs the marginal mandibular branch of the facial nerve, which moves the lower lip.