TMJ Anatomy and Histology Quiz

TMJ (Temporomandibular Joint) Anatomy

• The TMJ is the joint between the temporal bone of the skull and the condyle of the mandible, responsible for jaw movement.

Articular Surfaces

• The temporal bone articulates from above, featuring: • Articular eminence and glenoid fossa • Fibrous covering with uneven thickness (thin at glenoid fossa, thick at eminence) • Bone structure consisting of thin layer of compact bone covering cancellous bone
• The condylar head articulates from below, featuring: • Fibrous covering ("Fibrocartilage") divided into two parts: • Fibrous layer (even thickness, composed of strong bundles of collagen type I fibers) • Cartilaginous plate (hyaline cartilage layer, acts as a growth center until age 20, with ossification taking place in the deep layer of the fibrocartilage) • Bone structure consisting of thin layer of compact bone covering cancellous bone, with cancellous bone trabeculae arranged in a radiating manner to provide maximum strength

Articular Disc

• The articular disc is an oval plate dividing the joint cavity into upper and lower compartments.
• Features of the disc: • Upper surface: concavo-convex • Lower surface: concave • Well vascularized and innervated at its periphery, but not in its central portion • Anteriorly inserted into the superior head of lateral pterygoid muscles • Posteriorly connected to the capsule by the retro-diskal pad (well vascularized and innervated) • Medial and lateral portions blend with the joint capsule and poles of the condyle, allowing the disc and condyle to move as a single unit
• Histological structure: • Collagen type I fibers arranged loosely and randomly, except in the central portion where they are arranged more tightly and organized • Few elastic fibers

Capsular Ligament

• Function: restricts movement of the disc away from the condyle, allowing smooth and synchronous motion of the condyle/disc.
• Composition: consists of an outer fibrous layer and an inner synovial layer (synovial membrane).

Joint Cavity

• Divided by the articular disc into upper and lower compartments.
• Lined by synovial membrane, which lines the entire capsule, except for the articular surfaces and disc (except its posterior region).
• Function of the synovial membrane: • Production of synovial fluid • Varying cell types (type A Macrophage like...)