بسم الله الرحمن الرحيم

Tempromandibular joint Bilateral synovial joint It is the articulation of the condyle with the articular fossa and articular eminence of the temporal bone.

TMJ is consisted of: 1-Bones of the joint *Mandibular condyle *Temporal bone…… articular fossa & articular eminence 2-Articular disc 3-Capsular ligament 4-Joint cavity ( synovial membrane)

Bones of the joint It consists of two bones: * The condyle *The articular eminence and articular fossa of the temporal bone.

Compact bone A- The condyle Spongy bone Composed 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

The fibrous covering of the condyle (fibrocartilage) Its superficial layer consists of: Network of strong collagenous f. & very occasionally elastic fibers and fibroblasts. Cartilage cells (chondrocytes) may be present that increase in number by age.

The 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

During 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 years Fibrocartilage Layer (fibrous covering)

B-temporal bone Articular eminence Articular (glenoid) fossa

The 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 disc The condyle

In 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 surface Intermediate transitional layer-fibers run in complex fashion outer layer - fibers parallel to the surface.

Fibroblasts & 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.

Articular disc

The articular disc: Is Oval Fused with the capsule Separates the cavity into two compartments -Upper surface is concavoconvex ( to fit AE & GF) -Lower surface is concave ( to fit head of the condyle)

Histologically Formed 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.

The disc is divided into three bands: Posterior band Anterior Band Intermediate band

Anterior band – split into 2 lamellae -Upper lamella attached to articular eminence -Lower lamella attached to anterior surface of the condylar head fibers of superior head of the lateral pterygoid muscle inserted in-between

Upper lamella Anterior Lower lamella

Intermediate band: Thinnest central region which is avascular and has no innervation.  This zone is composed of fibrous connective tissue and is devoid of cells .

Posterior 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 elastic fibers. 

Upper lamella Posterior Lower lamella

Fibrous capsule

Anatomy It 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.

The capsular ligament is attached : Superiorly………to the temporal bone Inferiorly………..to the neck of condyle

Histology

The 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.

Synovial membrane: 1-cellular intima Fiber free matrix -fibroblast-like cells (type B) -macrophage-like cells (type A) -intermediate cells 2-vascular subintima Loose C.T. -fibroblast,macrophage,mast cells,fat cells -blood ves.

The joint cavity

Synovial fluid is viscous and consists of plasma ,protein ,mucin. Functions 1-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.  

Innervation and blood supply

Sensory innervation : branches of the mandibular division of the trigeminal nerve 1-auriculotemporal nerve 2- masseteric nerve. 3-posterior deep temporal nerve.

Blood supply Internal maxillary artery: -deep auricular -superficial temporal --Pterygoid plexus

Movements 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