Tmj.... Final...

TEMPEROMANDIBULAR JOINT

INTRODUCTION 



Joint or articulation between movable mandible & fixed temporal bone of cranium. Ginglimodiarthroidal synovial joint

ANATOMY OF TMJ   

2 bony structures Interposed fibrous disc Enclosed in a fibrous capsule

BONES FORMING ARTICULAR SURFACE CONDYLE  Long axis inclines backward & medially  Articulating surface – convex located on superior & ant surface of head of condyle Triangular depression on ant border – insertion of lateral pterygoid muscle 

 







Articular surface of temporal bone Posterior part – concave – articular fossa Anterior part – convex – articular tubercle / eminence Articular fossa – ovoid depression anterior to auditory canal Articular eminence – bony prominence located anterior to

HISTOLOGY OF ARTICULATING SURFACES 





Head of condyle – dense compact bone with cancellous bone in the center Articular fossa lined by thin layer of compact bone Articular eminence – core of cancellous bone covered by a layer of compact bone

ARTICULAR FIBROUS COVERING 4 distinct layers 1] Superficial zone – articular zone  Composed of fibrous tissue  Fibroblasts scattered in avascular layer of type I collagen fibers arranged in bundles oriented parallel to articular surface  c/t contains few cartilage cells 

2] Proliferative zone – highly cellular  Composed of undifferentated mesenchymal cells  Remodeling & repair of articular surfaces 3] Fibrocartilagenous zone – bundles of collagen fibers arranged in crossing pattern & some in radiating pattern  Resistance against compressive or lateral forces 4] Calcifed zone – made of chondrocytes &

ARTICULAR CAPSULE  





Dense collagenous sheet of tissue Circumferentially attached to rim of glenoid fossa & articular eminence above & neck of condyle below Ant portion of capsule attached above – ascending slope of articular eminence - Below to ant margin of condyle Posterior portion attached above squamotympanic fissure - Below to post margin of ramus of mand





Anterolateral aspect of capsule thickened to form temporomandibular ligament Post fibers of capsule blend with articular disc

HISTOLOGY OF ARTICULAR CAPSULE  

Outer fibrous layer Inner synovial membrane

Synovial membrane 



Inner surface – thrown into folds villi like process 2 layers inner cellular intimal layer vascular subintimal layer

Subintimal layer 

 

Loose c/t cont blood vessels, scattered fibroblasts, macrophages, mast cells Elastic fibers Collagen fibers

Intimal layer    





1-4 layer of synovial cells Amorphous intercellular matrix 3 types of cells Type A cells [ macrophage like cells] – irregular outline with plasma membrane invaginations. Phagocytic properties Type B cells [ fibroblast like or secretory S cells ] – involved in synthesis of hyaluronic acid Third type with cellular morphology in between the other two

Joint cavity    

Synovial fluid Proteins & hyaluronic acid Synovial cells Defence cells

Functions of synovial membrane     

Lubrication Nutritive Regulatory Secretory Phagocytic

Articular disc 





Tough biconcave pad of dense fibrous c/t located between condyle & articular surface of temporal bone. Thin in the center & thicker towards periphery 4 distinct regions – anterior band intermediate zone posterior band



 

Upper contour concave ant & convex posteriorly Lower surface of disc – Concave Ant disc divided into 2 lamellae – upper fuses with capsule & periosteum of articular eminence - lower attaches to neck of condyle

 





Post disc divided into 2 lamellae Upper consisting fibrous & elastic tissue and fusing with capsule & inserting into squamotympanic fissure Lower non elastic composed of collagen & blends with periosteum of neck of condyle. Between lamellae loose highly vasculsar c/t – bilaminar zone







Joint space – upper – temprodiscal - lower – condylodiscal Lower joint space – hinge movement Upper joint space – translatory movement

Histology of articular disc 

   

Dense fibrous tissue with tightly packed collagen fibers Fibroblasts Elastic fibers Periphery vascular Central part devoid of vessels & nerves

Functions of articular disc 

     



Divides joint cavity into 2 compartmrnts permitting different types of mandibular movements Reduces physical wear Shock absorption Stabilises the condyle Regulates movts of condyles Assists in lubricating mechanism Prevents undue forward movt of condyle Distributes weight preventing wear

Ligaments of TMJ   

Capsular ligament Temporomandibular ligament Accessory ligaments Sphenomandibular ligament Stylomandibular ligament

MOVEMENTS

OF

TMJ