The mandible is the only movable cranial bone. It is a single bone connected to the skull at both temporomandibular joints. Like the maxilla, it is also a part of the viscerocranium of the skull. The mandible forms the lower jaw, and it presents with three parts:

• Body of the mandible
• Ramus of the mandible (paired)

Body of mandible

The body of the mandible is the anterior central part of the lower jawbone. It has a curved shape and can be subdivided into two smaller portions: 

• Base of the mandible
• Alveolar process of the mandible

The body of the mandible has two surfaces (external and internal) and two borders (superior or alveolar and inferior).

Base of mandible

The base of the mandible the inferior, thickened part of the body, and it has external and internal surfaces.

The features on the external surface of the mandibular base are:

• Mental protuberance - a prominence on the outer surface of the mandible that forms the chin;
• Mental tubercle (2) - a prominence on either side of the mental protuberance;
• Mental foramen (2) - an opening in the base located below the second premolar; it serves as the passage for the mental nerve (a branch of the inferior alveolar nerve, which arises from the mandibular nerve (CN V3)), as well as it is a pressure point for the mandibular nerve - the third branch of the trigeminal nerve (CN V);  besides nerves, through the canal also goes the mental artery, which is a branch of the inferior alveolar artery from the maxillary artery.

The landmarks found on the internal surface of the mandibular base include the following:

• Mental spine - a bony elevation projecting towards the tongue; it is the origin site of the genioglossus and geniohyoid muscles;
• Digastric fossa (2) - an oval depression on the inferior aspect of the internal surface of the mandibular base; it is located on either side of the mental spine; serves for the attachment of the anterior belly of the digastric muscle;
• Mylohyoid groove (2) - an oblique ridge extending from the posterosuperior to the anteroinferior aspect of the inner surface; it is the origin site of the mylohyoid muscle; its posterior part is also the origin site of the mylopharyngeal part of the superior pharyngeal constrictor muscle; the ridge above the mylohyoid groove is known as the mylohyoid line;
• Sublingual fossa (2) - a depression on the sides of the mental spine above the medial end of the mylohyoid line; it houses the sublingual gland;
• Submandibular fossa (2) - a depression located on the sides of the body below the mylohyoid line; it houses the submandibular gland.

Alveolar process of mandible

The alveolar process of the mandible is the superior crested portion of the body of the mandible. It surrounds and supports the lower teeth. 

Its curved free margin is called the alveolar arch. The alveolar arch of the mandible (like the alveolar arch formed by the maxillae) features the following landmarks:

• Dental alveoli - sockets in the alveolar process for the roots of the teeth;
• Interalveolar septa - bony ridges between adjacent dental alveoli;
• Interradicular septa - bony ridges forming compartments in dental alveoli for the roots of the teeth;
• Alveolar yokes (juga alveolaria) - eminences on the outer surface of the mandible produced by the projections of the dental alveoli.

Ramus of mandible

The rami of the mandible are situated on the right and left side of the mandible. They extend upward from the body of the mandible. Each ramus of the mandible features several landmarks:

• Angle of the mandible - the angle between the body and ramus of the mandible;
• The superior part of the ramus has two processes:
  • Condylar process - an articular process that articulates with the temporal bone at the temporomandibular joint; it has three features:
    • Head of the mandible - the articular part of the process;
    • Neck of the mandible - a narrow segment below the head of the mandible;
    • Pterygoid fovea - an anteromedial pit below the head of the mandible; it is the site where the lateral pterygoid muscle attaches;
  • Coronoid process - a flattened process located anteriorly to the condylar process; it serves as an insertion site for the temporal muscle;
  • Mandibular notch - a curved depression between both processes.

Like the body of the mandible, the ramus also has internal and external surfaces.

The internal surface of the ramus features the following landmarks:

• Mandibular foramen - an opening leading into the mandibular canal that serves as a bony passage for the inferior alveolar artery, inferior alveolar vein and inferior alveolar nerve;
• Lingula - a triangular-shaped bony ridge extending superior from the mandibular foramen;  it is also known as the Spix's spine; 
• Mylohyoid groove - a groove on the internal surface of the mandible extending forward and downward from the mandibular foramen; it transmits the mylohyoid nerve (a branch of the inferior alveolar nerve) and the mylohyoid branch of the inferior alveolar artery (from the maxillary artery);
• Pterygoid tuberosity - a roughened area present on the internal surface of the mandibular ramus near the angle of the mandible; it serves as the attachment site for the medial pterygoid muscle.

The external surface of the mandibular ramus presents the masseteric tuberosity - a roughened area present near the angle of the mandible. This tuberosity is the attachment site for the masseter muscle.