Anatomia da Articulação Temporomandibular (ATM) PARTE 1

Summary

In this detailed lecture on the temporomandibular joint (TMJ), Professor Marcelle Alvarez Rossi of UFBA explains the anatomy and function of this vital joint. The TMJ is classified as a synovial, bicondylar joint and involves important structures such as the mandibular head, the mandibular fossa, and the articular tubercle. The lecture explores the surfaces of the joint, the fibrocartilage disc, and the role of the synovial fluid in lubrication and nutrition. The complexity of the joint’s bilateral nature, along with its cartilage and capsule structures, are discussed, providing a thorough understanding of its anatomical and functional significance in relation to the jaw's movement.

Takeaways

• 😀 The temporomandibular joint (TMJ) is classified as a synovial joint, which allows for greater mobility between the bones.
• 😀 TMJ is functionally classified as a bicondylar synovial joint due to the convex-convex relationship between the mandibular head and the temporal bone.
• 😀 The TMJ is bilateral, meaning it consists of two separate joints on either side of the head, one for each temporal bone.
• 😀 The articular surfaces in the TMJ include the mandibular head, the mandibular fossa, and the articular tubercle.
• 😀 The mandibular head is an elliptical convex surface, while the fossa is concave and located within the temporal bone.
• 😀 The TMJ's articular cartilage is fibrocartilage, unlike the hyaline cartilage found in most synovial joints, offering higher resistance and some regenerative potential.
• 😀 The thickness of the articular cartilage in the TMJ varies: thinner in the mandibular fossa and thicker near the posterior and inferior areas of the articular tubercle.
• 😀 The TMJ is encased in a fibrous capsule that helps hold the joint together, preventing leakage of synovial fluid.
• 😀 The synovial membrane inside the capsule produces synovial fluid, which nourishes the cartilage and lubricates the joint surfaces to minimize friction.
• 😀 An accessory structure in the TMJ is the articular disc, which helps to improve the fit between the mandibular head and the articular tubercle, as well as absorb impact during movements.

Q & A

What is the anatomical classification of the temporomandibular joint (TMJ)?

The TMJ is classified as a synovial joint, specifically a bicondylar synovial joint due to the elliptical, convex shape of both the mandibular head and the articular tubercle of the temporal bone. It also has a bilateral classification, as there are two joints, one on each side of the body.

How does the TMJ differ from other synovial joints?

The TMJ is unique among synovial joints because it has a more complex structure, being bilateral and having both a condylar and bicondylar classification. Additionally, it contains an articular disc made of fibrocartilage, unlike many other joints that only contain hyaline cartilage.

What are the main articular surfaces of the TMJ?

The main articular surfaces of the TMJ include the mandibular head (part of the condylar process), the mandibular fossa of the temporal bone, and the articular tubercle, which all contribute to the joint's mobility.

What is the role of the articular disc in the TMJ?

The articular disc, made of fibrocartilage, improves the adaptation between the surfaces of the TMJ during movements such as translation. It also serves to cushion impacts, especially during strong jaw movements, reducing the stress on the joint.

How does the articular disc contribute to the TMJ's function?

The disc improves the congruency between the mandibular head and the articular tubercle, ensuring smoother motion during translation. It also acts as a shock absorber, protecting the joint from the impact forces generated during actions like chewing.

What is the significance of the fibrous layer of the TMJ capsule?

The fibrous layer of the TMJ capsule provides structural stability and helps contain the synovial fluid within the joint. It also prevents leakage of the synovial fluid and supports the articular disc and the ligaments associated with the joint.

How does the synovial fluid in the TMJ aid in its function?

The synovial fluid in the TMJ lubricates the articular surfaces, reducing friction and allowing for smooth, efficient movement. It also nourishes the articular cartilage, contributing to its maintenance and repair.

What is the role of the lateral pterygoid muscle in the TMJ?

The lateral pterygoid muscle plays a crucial role in the movement of the TMJ, particularly in its ability to control the position and movement of the articular disc. It assists in stabilizing the joint and facilitating movements such as protrusion and lateral movements of the jaw.

What is the relationship between the mandibular head and the articular tubercle during jaw movements?

During jaw movements, particularly in translation, the mandibular head moves forward and downward, potentially surpassing the top of the articular tubercle and reaching the infratemporal surface. This movement does not necessarily lead to dislocation and depends on the condition of the surrounding muscles and ligaments.

How is the TMJ's cartilage different from other synovial joints?

The TMJ's articular cartilage is made of fibrocartilage rather than hyaline cartilage. This makes it more resilient and capable of withstanding greater stress and forces. Additionally, fibrocartilage has a higher regenerative potential compared to hyaline cartilage.