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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