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 articular fossa

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 layers1] 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 surfaces3] Fibrocartilagenous zone – bundles of collagen

fibers arranged in crossing pattern & some in radiating pattern

Resistance against compressive or lateral forces4] Calcifed zone – made of chondrocytes &

chondroblasts Active site for remodelling activity

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 bilaminar region

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

OF

TMJ

MOVEMENTS