Anatomy of the lower jaw

The lower jaw (mandibula) is the only movable bone of the skull. It is involved in chewing, speaking, swallowing and forms the lower part of the facial contour. The strength of the lower jaw is second only to the femur.

Building

The lower jaw consists of a horseshoe-shaped body and two branches rising upward. On the body there is an alveolar part with 16 tooth sockets (in an adult). On the outside of the body there is a chin protuberance - an anatomical feature unique to humans among primates.

Each branch ends in two branches:

• Coronoid process - place of attachment of the temporal muscle
• Condylar process - forms the articular head for the temporomandibular joint (TMJ)

Between the processes there is a notch of the lower jaw, through which blood vessels and nerves pass.

Temporomandibular joint

The TMJ is one of the most complex joints in the body. It is combined: the right and left joints work simultaneously. Inside the joint there is an articular disc that divides the cavity into two floors. Thanks to this device, movements in three planes are possible: opening the mouth, lateral displacement and forward movement.

TMJ dysfunction is a common problem that causes clicking, pain, and limited mouth opening. The cause is often a malocclusion or chronic spasm of the masticatory muscles.

Chewing muscles

Four pairs of muscles move the lower jaw:

• Masticatory muscle (m. masseter) - the strongest, closes the mouth
• Temporal muscle (m. temporalis) - also closes the mouth and pulls the jaw back
• Medial pterygoid - raises the jaw and moves it to the side
• Lateral pterygoid - opens the mouth and moves the jaw forward

The chewing muscle is capable of developing a force of up to 70 kg at the level of the molars - this is one of the strongest indicators among the muscles of the human body.

Clinical significance

Fractures of the mandible account for up to 70% of all facial fractures. Typical fracture sites are the mental foramen area, the angle of the jaw, and the condylar process. Knowledge of the course of the mandibular canal (where the nerve and artery pass) is critical in dental surgery and anesthesia.

You can examine in detail the structure of the lower jaw, the temporomandibular joint and the masticatory muscles in the Humio application - an interactive 3D model allows you to isolate each structure.