The mandible (mandibula) or the lower jaw is the sole mobile bone of the skull. It’s action is indispensable for mastication. Moreover, the mandible is the largest and toughest bone of the splanchnocranium. It is made up of two parts: body of the mandible, and ramus of the mandible.
Body of the mandible (corpus mandibulae) is the horizontal component, within the coronal plane, with the base of mandible, and alveolar part which carries the teeth.
The alveolar part (pars alveolaris) contains the following notable structures:
- Alveolar arch (arcus alveolaris) with the:
- Dental alveoli (alveoli dentales).
- Interalveolar septa (septa alveolaris).
- Interradicular septa (septa interradicularia).
- Alveolar yokes (juga alveolaria), which is the eminent part of the external surface corresponding with depressions.
- Retromolar fossa (fossa retromolaris).
- Retromolar triangle (trigonum retromolare), which is located behind the third molar tooth.
The base of mandible is site of attachment for the digastric muscle medially.
The body of mandible has two distinguished surfaces, external, and internal.
External surface has the following bony landmarks:
- Mental protuberance (protuberantia mentalis) which is the triangular eminent surface with the mental tubercle (tuberculum mentale)which is located laterally to the protuberance.
- Mental foramen (foramen mentale) which is located between 1st and 2nd premolar. It is the opening of the mandibular canal, which transmits the mental nerve and vessels.
- Oblique line (linea obliqua) which runs backward and upwards from the mental foramen.
Internal surface has the following bony landmarks:
- Mental spine (spina mentalis) is located on the midline of the body and projects posteriorly. Sometimes it is bifurcated.
- Digastric fossa (fossa digastrica) which is situated near the inferior border and it created due to the attachment place of the anterior belly of the digastric muscle.
- Mylohyoid line (linea mylohyoidea) which runs backward and upward, forming an attachment place for the mylohyoid muscle.
- Submandibular fossa (fovea submandibularis) located beneath the mylohyoid line, and it is a notable depression caused by the submandibular gland.
- Sublingual fossa (fovea sublingualis) which lies above the mylohyoid line.
Ramus of mandible (ramus mandibulae) is the vertical component of the mandible within the sagittal plane.
It has the:
External surface has the:
- Masseteric tuberosity (tuberositas masseterica).
- Angle of mandible (angulus mandibulae).
Internal surface has the:
- Pterygoid tuberosity (tuberositas pterygoidea)
- Mandibular foramen (foramen mandibulae) with:
- Mandibular lingula (lingula mandibulae), projects upwards and partly protects the inferior alveolar nerve and vessels, which enters the mandibular canal. It is also the attachment point for the sphenomandibular ligament.
- Mandibular canal (canalis mandibulae).
- Mylohyoid groove (sulcus mylohyoideus), starts at the level of the mandibular foramen, continues past the posterior part of the mylohyoid line. It is produced by the mylohyoid nerve and vessels which passes along it.
Condylar process (processus condylaris) which is composed of the:
- Head of mandible (caput mandibulae) with the articular surface.
- Neck of mandible (collum mandibulae).
- Pterygoid fovea (fovea pterygoidea) on the anterior surface of the neck, and serves as the attachment place of the medial pterygoid muscle.
- Coronoid process (processus coronoideus).
- Mandibular notch (incisura mandibulae) which is situated between the condylar process and coronoid process.