TMJ

for dental students

1. Tempro-mandibular joint Dr: 3mmar Mobile: [phone] F.B: [email protected]

2. Contents of chapter 1- definition. 2- anatomy of TMJ : ( articular disc , upper , lower compartments , capsule & synovial fluid). 3- histology of TMJ ( bone of joints & articular disc & capsular ligament & joint cavity). 4- synovial fluid , its functions. 5- innervation of TMJ. 6- blood supply of TMJ 7- disorder of TMJ. ( ankylosis & dislocation ). 8- age changes. 9- development of TMJ.

3. 1- definition. TMJ is bi-lateral synovial movable joint of modified hing type between condylar head of mandibule & glenoid fossa , atricular eminence of temporal bone. TMJ Articular eminence Glenoid fossa Condylar head

4. 2- anatomy of TMJ ( condylar head , articular fossa , eminence , disc , capsule ) . Tmj formed by : articulation between upper part , lower part. 1- upper part: its articular eminence , anterior part of glenoid fossa . 2- lower part: head of condyle . In between upper , lower parts there is fibrous disc that’s divide the TMJ into upper & lower compartments. Its called articular disk . N.B: joint which has one cavity its have one movement just opening , closing but joint which two cavities its movements are multiple

5. Articular capsule: its avascular non-elastic capsule which attached to : anterior: to ascending slope of articular eminence . posterior: to lips of squamous tympanic fissuer . superiorly: to glenoid fossa . inferiorly to neck of condyle . TMJ capsule

6. 3- histology of TMJ A) Bones of joint 1- condyle . 2- glenoid fossa , articular eminence. B) Articular disc. C Capsular ligament. D) Joint cavity. , synovial fluid .

7. A) Bones of joint 1- condyle : l  its formed of cancellous bone covered by thin layer of compact bone. bone trabecula of spongy bone are radiating from neck of condyle to reach the cortex at right angle (maximum strength). . by age wide marrow space will decrease by thickening of bone trabecula . & this space may replaced by fatty marrow. Condyle is covered by a layer 1-2 microne thick elastic fibrous tissue which contains:- 1- network of type one collage fibers. 2- some elastic fibers. 3- fibroblast. 4- numerous UMC. 5- cartilage cells ( chondro-cyte ) N.B: This layer called : lamina splendens

8. Histological Structure of TMJ Trabeculae radiate from the center of condyle and reach the surface at right angles fibrous C.T. fibrous C.T. inner zone &. outer zone synovial membrane fibrous C.T.

9. 2- articular eminence , articular fossa . . A) articular eminence: its formed of spongy bone which covered by thin layer of compact bone.  its covered by thick fiberes arranged in 2 layers: 1. inner layer: fiberes are at right angle to bone surface. 2. outer layer: fiberes are parallel to bone surface. B ) articular fossa : its formed of thin layer of compact bon.  its covered by thin fibrous tissue.

10. A: Articular disc B: Glenoid fossa C: Condyle

11. Articular disc .  Its an oval plate whose periphery fused with the capsular ligament , its center is thin & sometimes is perforated .  upper surface: is concave convex , fit to articular eminence , fossa .  lower surface: is concave , fit to head of condyle . .  histologically : * its formed of: dens , avascular , tightly packed type one collagen fibrous tissue which run in anterio -posterior direction. * few elastic fibers. * fibroblast with elongated process. * chondrocyte with advancing age. concave concave convex

12. Anteriorly the disc divides into two lamellae:- upper lamellae: attached to anterior edge of articular eminence. lower lamellae: attached to anterior surface of the condylar head. Posteriorly the disc divides into two lamellae:- . upper lamellae : consist of loose C.T containing B.V , nerves & elastic fibers that blend posteriorly with articular capsule . lower lamellae : its thin extension which attach to posterior surface of the neck of condyle . N.B: 1- medially , laterally the disc blend with the articular capsule where its attached to the medial , lateral surface of the condyle i.e. The head of condyle , the disc move as one unit. ( transtional movement) 2- The disk divides the joint space into: a. Condylo-diskal compartment (lower one), permits hinge (rotation) movement. b. Temporo-diskal compartment (upper one), p ermits translatory movement

13. C) Capsular ligament .  Its fibrous s  Attach 1- anteriorly : to articular eminence 2- posteriorly to lips of squamotympanic fissuer 3- superiorly: to glenoid fossa . 4- inferiorly to neck of condyle . 5- laterally : its thickned to form tempro-mandibular ligament which is traingular in shape . the base of triangle attach to zygomatic arch, apex attach to lateral wall of the neck of condyle .  histologically : tha capsule consist of: 1- outer fibrous layer. 2- inner synovial membrane * synovial membrane: its thin 2 layers of C.T rich in B.V , lined the capsule & have villi protruded into the joint cavity.

14. Synovial membrane

15. Joint cavity Its contains the synovial fluid , surrounded by synovial membrane. synovial membrane is formed of 2 layers:- 1- cellular intima : its facing the joint cavity , formed of one to four layers of synovial cells embeded in amorphous fibers-free inter-cellular matrix 2- vascular sub- intima : which blends with the fibrous layer of capsule , its formed of vascular loose C.T with cells ( fibroblast , fat cells , mast cells & macrophage)

16. Synovial membrane

17. Synovial fluid Its produced by synovial membrane intimal cells. Formed of viscous fluid. (plasma , protein & mucin ), containing varying types of cells ( monocyte , lymphocyte , sometimes multi-nuclear leukocyte & macrophae ). Functions Synovial fluid Provide lubrication to joint surfaces to reduce the wear during joint function. Provide nutrition to disc , articular surfaces. Removal of foreign material ( phagocytosis ).

18. 5- innervation of TMJ TMJ is innervated by:- 1. auriculo -temporal nerve. 2. masseteric nerve. 3. deep temporal nerve. 4. there are several types of nerve endings including: a- ruggmis corpuscles: for dynamic , static balance . b- pacinis corpuscles : register changes in pressure , vibration. 6- blood supply of TMJ . Arterial supply come from external carotid artery through: 1- deep auricular branch. 2- superfacial temporal artiries . 3- anterior tympanic artries . 4- ascending pharyngyal artery . .  Drainage is done through pterygoid plexus

19. 7- disorder of TMJ 1- ankylosis : its bony union between condylar head , glenoid fossa . cause : infection or truma . result in: disability of patient to open his mouth. 2- dislocation: its displacement of condylar head from its postion in the glenoid fossa * this displacement is mostly anterior displacement caused by :- 1- wide mouth opening. 2- small or short flat articular eminence. 3- weak capsular ligament. * its rarely occurs as posterior diplacement . * this displacement may be uni -lateral or bi-lateral.

20. Age Changes of TMJ Flattening of the condyle Thick fibrous covering of the condyle with chondroid changes Osteoporosis of the underlying bone Thining of the cartilagenous zone of the condyle Thin articular disc with hyalinization and chondroid changes Synovial folds and villi increase and become fibrotic Decreased extensibility of the disc and capsule decreased synovial fluid loss of lubrication Dysfunction of TMJ in old age Decreased nerves in disc and capsule

21. 9- development of TMJ. Begins at 10 weeks of gestation by appearance of 2 distinct mesenchymal condensation : 1. The temporal blastema (appears first) 2. The condylar blastema .

22. Thanks Dr: 3mmar