TEMPROMANDIBULAR JOINT

Menatalla M. Elhindawy

Temporomandibular JointTMJ

Classification of joints

Fibrous joints

Cartilaginous joints

Synovial Joints


SUTURAL Limited or no movement. The articulating surfaces

are covered with osteogenic layer to allow for bone formation.

GOMPHOSIS The movement is only

restricted to intrusion and recovery.

SYNDEMOSIS Intraostious ligament joins

between 2 bones: Radius and Ulna; Tibia and Fibula.

This ligament allows limited movement.

Fibrous Joint


Limited or no movement

cartilaginous Joint

Classification of joints Allow significant movement. Articular surfaces covered with

hyaline cartilage. Capsulated joint. The capsule forms a cavity;

filled by synovial fluid formed by synovial membrane.

The joint cavity may be divided by an articular disk.

Classified according to number of articulating surfaces or shape of articulating surfaces.

Synovial Joint

Temporomandibular JointTMJ

Development of TMJ

Development of TMJ At 12th WIUL, 2

distinct mesenchymal condensations appear

condylar then temporal blastemata.

Both are apart Condylar blastema grows rapidly and

close the gap

Ossification of temporal blastema

while condylar remains mesenchyme

A cleft is formed above the condylar blastema forming

inferior joint cavity

A 2nd cleft is formed in relation to temporal

blastema after differentiation of

condylar into cartilage

Development of TMJ

Primitive disk is formed

Developing head of lat. Ptegoid ms is attached ot the

ant part of the disk

The disk is attached to the mallous of the

middle ear

Once ptregotympanic fissure is formed this connection is

lost

Early muscle contraction is

important for joint cavitation

Development of TMJ

TMJ

Articulating surfaces

Condylar head

Temporal bone

Articular disk

Capsular ligament

Joint cavity

TMJ.. Articulating surfacesA. Temporal bone

• Articular eminence and glenoid fossa.

• Present on the under surface of the squamous part of the temporal bone.

TMJ.. Articulating surfacesA. Temporal bone A. Fibrous covering “Fibrocartilage”

Un- even thickness.Thin at the glenoid fossa.

Thick at the eminence. Its outer layer fibers run parallel

to the surface and are densely arranged; while in deeper layers it is perpendicular to the surface.

TMJ.. Articulating surfacesA. Temporal bone B. Bone

The glenoid fossa is formed of a thin layer of compact bone.

The articular eminence is formed of thin layer of compact bone covering cancellous bone.

C. Cells No continuous cell layer on the

free surface of the fibrocartilage. Fibroblasts are flattened. Chondrocytes are isolated or in

small groups.

TMJ.. Articulating surfacesB. condylar head

Forms the articulation from below

TMJ.. Articulating surfacesB. condylar head A. Fibrous covering “Fibrocartilage”

Even thickness; composed of: I. Superficial layer… strong bundles

collagen type I fibers, some elastic fibers and fibroblasts inbetween bundles. “chondrocytes may present and may increase with age”

II. Deep layer “reserve cell zone”… rich in UDMCs present as long as hyaline cartilage is present.

By EM.. A layer called lamina splendens is found above the fibrous layer; 1-2 u with smooth outer surface and irregular inner one.

TMJ.. Articulating surfacesB. condylar head B. Bone

thin layer of compact bone covering the cancellous bone.

Cancellous bone trabeculae arranged in a radiating manner to reach the surface at a right angle give maximum strength.

Large marrow spaces decreased with age to increase the thickness of trabeculae.

Red marrow turns to yellow with age.


Cartilagenous plateA layer of hyaline

cartilage is found underneath the fibrous covering.

This layer acts as a growth center until the age of 20.

Ossification takes place in the deep layer of the fibrocartilage.

Remnants of the cartilage may be found in old age.


It is not arranged in parallel rows of cells at the interface between the forming bone and cartilage, therefor it is referred to as a 2ry cartilage.

Its growth aids in the downward and forward growth of the mandible.

TMJ


Condylar head

Temporal bone

Articular disk

Capsular ligament

Joint cavity

TMJ.. Articular diskOval plate.Upper surface is concavo

convex.Lower surface is concave.Divide the joint cavity into:

upper large compartment.lower small compartment.

Medial and lateral blend with the joint capsule;

both blend with medial and lateral poles of the condyle.

so the disk and the condyle move as single unit.

TMJ.. Articular diskAnteriorly

Superior lamella: attached to anterior edge of articular eminence

Inferior Lamella: attached to the anterior surface of the condylar head.

Between the Superior and inferior lamella of superior head of lateral ptrygoid muscles are inserted.

TMJ.. Articular diskPostierioly

Superior lamella: attached to the posterior wall of the glenoid fossa and squamotympanic fissure.

Inferior lamella: attached to the posterior wall of the neck of the condyle.

TMJ.. Articular disk Fibers

Collagen type I arranged loosely and randomly EXCEPT in central portion they are arranged more tightly and organized.

Few elastic fibers. Fibroblasts are elongated and send

flat cytoplasmic processes between adjacent bundles.

Chondrocytes appear with advanced age and they increase the resentence and resilience of the fibrous tissue.

TMJ.. Articular disk The disk is well vascularized

and innervated at its periphery BUT not in its central portion

The disk is connected at its posterior margin to the capsule by the retrodiskal pad of loose connective tissue which is well vascularized and innervated.

TMJ


Condylar head

Temporal bone

Articular disk

Capsular ligament

Joint cavity

TMJ.. Capsular ligament Fibrous, non elastic membrane.Unites and convers bones of the

joint.Attachments

Anterior: articular eminence. Posterior: squamotympanic fissure. Superior: margins of the glenoid

fossa. Inferior: neck of the condyle.

Above the disk it is lax; below the disk it is tightly attached to the condyle.

The posterior part of the capsule is thickened to for the tempromandibular ligament.

TMJ.. Capsular ligament Surfaces

anterior surface is faint. Inner surface is smooth and

glistering because of the presence of the synovial membrane lining which doesn't extend on the articular surface of the disk, articular eminence or condyle.

TMJ.. Capsular ligament The TMJ ligament restricts the displacement of

the mandible in 3 different planes: It prevents medial dislocation of one

joint by preventing lateral dislocation of the other.

Its oblique component limits the amount of inferior displacement.

Its horizontal component limits or prevents the posterior displacement.

Sphenomandibular ligament: represents the residues of Meckle's cartilage.

Stylomandibular ligament: runs from spine of the sphenoid to the angle of the mandible.

TMJ.. Capsular ligament The capsule consists of:

outer fibrous layer.Inner synovial layer

(synovial membrane) It is a thin layer of connective tissue which is rich in blood supply.

It lines the entire capsule with folds and villi of membrane protruding into the joint cavity.

TMJ


Condylar head

Temporal bone

Articular disk

Capsular ligament

Joint cavity

TMJ.. Joint cavity

Consists of the synovial membrane which produce the synovial fluid.

Lines the entire capsule with folds or villi that protrude in the joint cavity.

These folds increase in number in cases of old age and pathologic conditions.

The synovial membrane doesn’t cover the articular surfaces or disk EXCEPT its posterior bilaminar region.

TMJ.. Joint cavity

Internal cells which don't form a contentious layer.

Consists of 2 layers: vascular subintema. cellular intema.

TMJ.. Joint cavity subintema

loose C.T containing vascular elements with scattered fibroblasts, macrophages, mast cells and fat cells.

Few elastic fibers. intema

1-4 layers of cells embedded in amorphous fiber free intercellular matrix.

3 types of cells I. A cells :they are mAcrophage like cellsII. B cells: they are fiBroblast like cells. III. Non A non B cells: they have cellular

morphology between A and B cells.

TMJ.. Joint cavityFunction of the synovial membraneI. Production of the synovial fluid. II. varying cell types such as monocytes,

Lymphocytes, free cynovial cells, polymorphnuclear leukocytes and macrophages.

III. Removal of foreign material.Function of the synovial fluid:

viscous fluid composed of Plasma with some added proteins and mucin.

IV. Nutrition to the disk and articular surfaces.V. Liquid environment for joint surfaces.VI. Lubrication to increase the efficiency and

decrease the erosion.

TMJ


Condylar head

Temporal bone

Articular disk

Capsular ligament

Joint cavity

TMJ.. Blood supply

Arterial supplyDeep auricular and superficial temporal branches of the maxillary artery.Venous drainagePtregoid plexus of veins

TMJ.. Nerve supply Sensory supply Auriculotemporal and masseteric branches of

mandibular branch of the trigeminal nerve.Proprioception

I. Ruffini’s endings static and dynamic mechanoreceptors.

II. Pancinian corpuscles dynamic mechanoreceptors.

III. Golgi tendon organs static mechanoreceptors.

IV. Free nerve endings pain receptors.Motor function is derived from joint muscles.

TMJ.. Clinical considerations I. AnkylosisIt is mostly bony union rarely fibrous of the condylar head to the glenoid fossa. It is mainly caused by trauma or infection. It results in disability of the patient to open his mouth. II. Dislocation It is displacement of the condylar head from its position in the glenoid fossa. It is mostly anterior displacement (rarely posterior) caused by wide mouth opening (during yawing), small or short flat articular eminence and weak capsular ligament. It may be uni-lateral or bi-lateral.III. Popping and clicking noisesThe joint has palpable irregularities and produces these noises. However, use of a stethoscope reveals that about 65%of TMJs produce some kind of sound. This feature may not require treatment.

Thank you..

TEMPROMANDIBULAR JOINT

Health & Medicine