Between these articular surfaces is the articular disc (or meniscus), which is a biconcave, transversely oval disc composed of dense fibrous connective tissue. Each TMJ is covered by a fibrous capsule. There are tight fibers connecting the mandible to the disc, and loose fibers which connect the disc to the temporal bone, meaning there are in effect 2 joint capsules, creating an upper joint space and a lower joint space, with the articular disc in between. The synovial membrane of the TMJ lines the inside of the fibrous capsule apart from the articular surfaces and the disc. This membrane secretes synovial fluid, which is both a lubricant to fill the joint spaces, and a means to convey nutrients to the tissues inside the joint. Behind the disc is loose vascular tissue termed the "bilaminar region" which serves as a posterior attachment for the disc and also fills with blood to fill the space created when the head of the condyle translates down the articular eminence. Due to its concave shape, sometimes the articular disc is described as having an anterior band, intermediate zone and a posterior band. When the mouth is opened, the initial movement of the mandibular condyle is rotational, and this involves mainly the lower joint space, and when the mouth is opened further, the movement of the condyle is translational, involving mainly the upper joint space. This translation movement is achieved by the condylar head sliding down the articular eminence, which constitutes the front border of the articular fossa.
Osteoma cutis is a cutaneous condition characterized by the presence of bone within the skin in the absence of a preexisting or associated lesion. : 529

See also
Calcinosis cutis
Skin lesion
List of cutaneous conditions

References


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