2Tempromandibular joint Bilateral synovial jointIt is the articulation of the condyle with the articular fossa and articular eminence of the temporal bone.
3TMJ is consisted of: 1-Bones of the joint *Mandibular condyle *Temporal bone……articular fossa & articulareminence2-Articular disc3-Capsular ligament4-Joint cavity ( synovial membrane)
4Bones of the joint It consists of two bones: * The condyle *The articular eminence and articular fossa of the temporal bone.
5Compact boneA- The condyleSpongy boneComposed of spongy bone covered by thin layer of compact bone.The trabeculae are grouped in such a way that they radiate from the neck of the condyle and reach cortex at right angle. This give maximum strength to the condyle.1
6The fibrous covering of the condyle (fibrocartilage) Its superficial layer consists of:Network of strong collagenous f. & very occasionallyelastic fibers and fibroblasts. Cartilage cells(chondrocytes) may be present that increase in numberby age.
7The deeper layer consists of: UMC as long as hyaline cartilage is present.* By E/M a lamina splendens layer was detected which is about (1-2 microns thick). It separates the collagen from the joint cavity (Synovial cavity).Joint cavity
8During the period of growth Underneath the fibrous covering……… There is a layer of hyaline cartilage which serves as an active growth center till the age of 20 yearsFibrocartilageLayer (fibrous covering)
11The glenoid fossa is formed only of thin layer of compact bone. The articular eminence is composed of spongy bone that is covered by a thin layer of compact bone.The glenoid fossa is formed only of thin layer of compact bone.The fibrous covering layer is thin in the g.fossa and thickened rapidly on the posterior slope of the articular eminence.The articular em.The discThe condyle
12In this region (post. slope of art. em In this region (post. slope of art.em.) the fibrous tissue is arranged in 3 zones:inner layer - collagen fibers perpendicular to the surfaceIntermediate transitional layer-fibers run in complex fashionouter layer - fibers parallel to the surface.
13Fibroblasts & chondrocytes (single or gathered in groups) form a type of fibrocartilage. This fibrocartilage become thin toward the glenoid fossa……it disappears at the depth of the glenoid fossa, here a layer of fibrous layer only is present.
16The articular disc:Is OvalFused with the capsuleSeparates the cavity intotwo compartments-Upper surface is concavoconvex ( to fit AE & GF)-Lower surface is concave ( to fit head of the condyle)
17HistologicallyFormed of dense avascular fibrous tissue that is formed of:-Tight collagen fs + some elastic fs + fibroblasts + some chondrocytes.The collagen fiber is of type I and form 80% of the disc weight and about 5% is glucosaminoglycans (chondritine sulphate that withstands compressive forces).The fibers are curled and wavy in shape to share in the biomechanical properties of the disc so allow the disc to stretch during compression.
18The disc is divided into three bands: Posterior bandAnterior BandIntermediate band
19Anterior band – split into 2 lamellae -Upper lamella attached to articular eminence-Lower lamella attached to anterior surface of the condylar headfibers of superior head of the lateral pterygoid muscle inserted in-between
21Intermediate band:Thinnest central region which is avascular and has no innervation. This zone is composed of fibrous connective tissue and is devoid of cells .
22Posterior band:This region attaches posteriorly by:Upper lamella (retrodiscal pad)-attaches to the capsular ligament-highly vascular and innervated.(loose CT ,elastic fs., BV., nerves)Lower lamella-attaches to the posterior aspect of the neck of the condyle.-consists mainly of collagenous fibers with no elasticfibers.
25AnatomyIt is a fibrous non-elastic membrane attached above to the squamotympanic fissure, the margin of the Glenoid fossa, and the articular eminence.Inferiorly, the capsule is attached to the neck of the condyle.The lateral aspect of the capsule is thickened to form a fan shaped ligament known as the tempro-mandibular ligament.
26The capsular ligament is attached : Superiorly………to the temporal boneInferiorly………..to the neck of condyle
28The capsule consists of : Outer fibrous layer-dense fibrous collagenous connective tissue.Inner synovial layer (synovial membrane)- lines the inner aspect of the capsule facing the two synovial spaces and has synovial villi.
31Synovial fluid is viscous and consists of plasma ,protein ,mucin. Functions1-To lubricate the joint surfaces; 2-As a source of nutrition for tissues lining cavity 3-To remove material (debris) from joint this is done by macrophages present in the synovial membrane adjacent to joint cavity.
35Movements of the joint Hinge - rotatory action Between condyle and articular disk Inferior synovial (joint) cavity Gliding - translatory action Between disk and articular eminence Superior synovial (joint) cavity