Chapter 8 - Section 8.2 - Study Guide - Assess Your Learning Outcomes - Page 271: 22

The two bones of the temporomandibular joint are the mandible of the face bones and the temporal bone of the cranium. The mandible is the lower jawbone-- originally two separate bones in infants and children but fused into one bone in adults. The structure of the mandible comprises the following parts: 1. The body: This is the anterior horizontal horse-shoe-shaped part that contains the lower teeth. 2. The ramus is the posterior part that runs in a slightly upwardly oblique direction relative to the body. 3. The angle: Body and ramus meet at the angle of the mandible. The masseter (muscle of mastication) inserts on the lateral surface of the angle. Distal from the orifice of the mouth the ramus of the mandible ends like a slightly irregular "U" with two branches/ processes; these are called the coronoid process (anterior branch, nearer to the body) and the condylar process (posterior branch, farther from the body). The coronoid process bears the point of insertion of the temporalis muscle. The condylar process bears the mandibular condyle which is a component of the temporomandibular joint. The mandibular condyle is a round process that articulates with the mandibular fossa of the temporal bone to form the temporomandibular joint (TMJ). The temporal bone The temporal bone is a cranial bone which can be palpated just above and anterior to the ear auricle. It forms the lower wall and part of the floor of the cranial cavity. It is divisible into four parts: (1) The squamous part-- palpable above the ear auricle; (2) the petrous part is located in the floor of the cranium where it separates the middle and posterior cranial fossae, and contains the middle ear and outer ear. (3) The tympanic part is a small ring of bone at the border of the external auditory meatus (external ear canal).(4) The mastoid part, which bears the mastoid process, is located posterior to the tympanic part. The temporal bone has two prominent features: the zygomatic process and the mandibular fossa. The mandibular fossa is the depression that articulates with the mandibular condyle of the mandible (ramus of) to form the temporomandibular joint (TMJ).

The articular surfaces of the TMJ are covered with fibrocartilage (unusual), and the the joint is stabilized by ligaments. These ligaments include the lateral ligament, the sphenomandibular ligament, and the stylomandibular ligament.. The mandible which is the strongest skull bone, is the only freely movable bone in the skull.