TemporoMandibular Joint Anatomy TMJ.pptx

TMJ

1. The temporomandibular joint(TMJ)

2. The temporomandibular joint (TMJ) It is a modified hinge type of synovial joint. It permits gliding (translation) and a small degree of rotation (pivoting) in addition to flexion (elevation ) and extension (depression) movements typical for hinge joints.

3. The articular surfaces of the TMJ The following bony articular surfaces are involved: The mandibular fossa and articular tubercle of the temporal bone superiorly, and The head of the mandible inferiorly.

4. The articular surfaces of the TMJ

5. The articular cavities The articular surfaces of the temporomandibular joint are covered by fibrocartilage . The joint is completely divided by a fibrous articular disc into two parts. The articular disc of the TMJ is attached at its periphery to the internal aspect of the fibrous capsule . This creates separate superior and inferior articular cavities, or compartments, These cavities are lined by separate superior and inferior synovial membranes.

6. Movements due to different joint cavities The lower part of the joint allows mainly the hinge-like depression and elevation of the mandible The upper part of the joint allows the head of the mandible to translocate forward (protrusion) onto the articular tubercle and backward (retraction) into the mandibular fossa.

7. Capsule of the TMJ

8. The synovial membrane It lines all non articular surfaces of the upper and lower compartments of the joint. It is attached to the margins of the articular disc.

9. Attachments of the synovial membrane It is attached: above along the anterior margin of the articular tubercle; laterally and medially along the margins of the articular fossa; posteriorly to the region of the tympanosquamous suture; below around the upper part of the neck of the mandible.

10. Ligaments of the TMJ Two extrinsic ligaments and the lateral ligament connect the mandible to the cranium. The lateral ligament The sphenomandibular The stylomandibular ligaments

11. The lateral ligament This is closest to the joint. A thickened part of the joint capsule forms the intrinsic lateral ligament of the TMJ. It runs diagonally backwards from the margin of the articular tubercle to the neck of the mandible. It strengthens the joint laterally . With the postglenoid tubercle it acts to prevent posterior dislocation of the joint.

12. The sphenomandibular ligament It is medial to the temporomandibular joint. It runs from the spine of the sphenoid bone at the base of the skull to the lingula on the medial side of the ramus of the mandible.

13. The stylomandibular ligament It passes from the styloid process of the temporal bone to the posterior margin and angle of the mandible. It is a thickening of the fibrous capsule of the parotid gland.

14. The masseter muscle

15. The lateral pterygoid

16. Temporalis

17. Medial pterygoids

18. Movements of TMJ Depression is generated by the D igastric , Geniohyoid , and Mylohyoid muscles on both sides. It is normally assisted by gravity. It involves forward movement of the head of the mandible onto the articular tubercle, the lateral pterygoid muscles are also involved.

19. Movements of TMJ Elevation is a very powerful movement generated by The temporalis , Masseter , and Medial pterygoid muscles It involves movement of the head of the mandible into the mandibular fossa.

20. Movements of TMJ Protraction is mainly achieved by The lateral pterygoid muscle. Some assistance is provided by the medial pterygoid .

21. Movements of TMJ Retraction is carried out by: The geniohyoid and Digastric muscles The posterior fibers of the temporalis muscles Deep fibers of the masseter muscles

22. Muscles producing movement at TMJ

23. A chewing or grinding motion occurs when the movements at the temporomandibular joint on one side are coordinated with a reciprocal set of movements at the joint on the other side . Movements of the mandible include depression, elevation, protrusion, and retraction.

24. Innervation of the muscles of mastication TMJ movements are produced chiefly by the muscles of mastication. These four muscles (temporal, masseter, and medial and lateral pterygoid muscles) develop from the mesoderm of the embryonic first pharyngeal arch ; consequently, They are all innervated by the nerve of that arch, the ( motor root of the) mandibular nerve (CN V3).

25. Clinical correlates Dislocation of TMJ Arthritis of TMJ