Oral bio tmj

Created by

Marium waqqas

Cards (52)

Classification of joints
Fibrous Joints
2. Cartilaginous Joints
3. Synovial Joints
What are fibrous joints
Two bones are connected by fibrous tissue
Types of fibrous joints
3 types
SUTURES
GOMPHOSIS
SYNDESMOSIS
What are sutures
Fibrous type joint, Little or no movement, function is to permit growth
What is syndesmosis
Fibrous type joint,Bony compartments are distant apart but joined by ligament in between
Permits limited movement
Radius & Ulna, Fibula & Tibia
What are cartilaginous joints
Permit little if any movements between bones involved.
Types of cartilaginous joints
Primary Cartilaginous Joint
Bone and cartilage are in direct apposition Example is Costochondral joint
Secondary Cartilaginous Joint
Bone--cartilage--fibrous tissue--cartilage—bone
Example is Pubic Symphysis
What are synovial joints
Permit significant movement Movements are initiated and effected by muscles
Two bones, each having articular surface covered by cartilage are united and surrounded by capsule, which creates a joint cavity
This cavity is filled by synovial fluid secreted by synovial membrane, that lines the nonarticulating surfaces
The joint cavity may be divided by disc
Types synovial joints
further classified as
Number of bones involved
 Uniaxial, Biaxial, Multi axial
2. Shape of articulating surfaces
 Planar, Ginglymoid (hinged), Pivot, Ball and socket
What is Hilton’s law 
“The muscles acting on the joint have the same nerve supply as the joint”
What is TMJ
The temporomandibular joint consists of the head of the condyle articulating with the glenoid fossa of the temporal bone.
 In front of the glenoid fossa is the articular eminence
 Between the head of the condyle and the temporal bone lies the articular disc
 Whole joint is enclosed in a fibrous capsule.
What are the articulate surfaces of TMJ
Four layers
The most superficial layer forms the articular surface and is composed of fibrous tissue collagen with few elastin fibres .Fibroblasts/fibrocytes are sparsely distributed
2. Beneath the surface layer is the more cell rich zone
3. Beneath cell rich zone is present fibrous layer in which a number of cells are rounded and have appearance of cartilage like cells this is layer is referred as fibrocartilaginous layer
4. Immediately covering bone is thin zone of calcified cartilage. This calcified cartilage is a remnant of secondary cartilage
What does articular disk contain
contains cells embedded in a matrix composed of fibers and ground substance.
collagen fibres mainly type 1 some elastin
Ground substance
cells
bloood vessel
Collagen in articular disc
The majority of fibers is Type I collagen although traces of other types are also
present
Small quantity of elastin fibers
Collagen fibers in the central thinner region of disk run in an anteroposterior direction
In the thicker anterior and posterior portions they run transversely (mediolateral) and superioinferiorly, giving fibers much more convoluted appearance.
Around peripherally fibers are arranged peripherally
In polarized light collagen fibers show dark and light bands indicating that they are wavy.
Ground substance in TMJ
Ground subsatnce 5% of dry wt.
The major glycosaminoglycan's are chondroitin sulphate and dermatan sulphate
By their anionic charge they absorb water and help resist compressive loading
cells in articular disc
Cells are numerous at the time of birth and become sparsely distributed in adults
They vary in appearance between flattened (fibroblast like) and round (chondrocyte like) rounded cartilage like appearance that is age related
The cells posses numerous fine processes extending for considerable distance
Occasionally cells may have rounded cartilage like appearance that is age related
Blood vessels in articular disc
Are present in the articular disk at time of birth
Majority are soon lost and bulk of disc especially the central region soon becomes avascular
Synovial membrane of TMJ 
Capsule is lined on its inner surface by a synovial membrane, that forms folds
or villi of membrane. These synovial villi project into joint space
These folds increase in number with age and are also more prominent in joints affected by a pathologic process. The synovial membrane does not cover the articular surfaces of the joint or the disk, except for its bilaminar posterior region
Layers of synovial membrane
a cellular intima resting on a
vascular subintima
Synovial membrane cells 
The cells comprising of superficial layer are of following types,
A fibroblast like cell: also known as Secretory Cell or B cell. It is rich in endoplasmic reticulum
A Macrophage like cell: its rich lysozymes and Golgi bodies with NO RER. Also known as A-Cell. It has phagocytic function
A third type has a morphology between A and B type
 As an age change, the amount of synovial fluid decreases and villous projections are seen to increase in number
Two articular surfaces of TMJ 
The join cavity is divided into upper and lower parts by intra articular disc or meniscus
Two articular surfaces,
The upper articular surface is formed by the parts of
temporal bone
 Articular eminence
 Anterior part of the mandibular fossa
2. The lower articular surface is formed by the head of the condyle
What is the shape of the intra-articular disc or meniscus?
It is an oval pad of fibrous tissue.
What is the structural shape of the intra-articular disc?
It is a saddle-shaped structure that separates the condyle and the temporal bone.
Describe the surfaces of the intra-articular disc.
The disc has a concavo-convex superior surface and a concave inferior surface.
Where are blood vessels found in the intra-articular disc?
Blood vessels are evident only at the periphery; the bulk is avascular.
What is the composition of the intra-articular disc?
It consists of coarse collagen fibers with interspersed fibroblastic cells.
How does the intra-articular disc divide the joint? 
Divides the joint into upper and lower compartments
Above it covers the slope of the articular eminence
Below it covers the condyle
How is the periphery of the intra-articular disc attached?
The periphery of the disc is attached to the fibrous capsule.
What is the posterior attachment of the intra-articular disc?
It is attached to the capsule by the bilaminar zone (retrodiscal pad).
How does the thickness of the intra-articular disc vary?
The disc varies in thickness
The thinner central intermediate zone separates thicker portions
The thicker portions are called the anterior band and the posterior band
What does the capsule of the joint do?
It envelops the whole joint.
Where is the capsule of the joint attached?
It is attached above to the articular surface and below to the neck of the condyle.
What type of tissue is associated with the posterior part of the capsule?
Thick, vascular but loosely arranged connective tissue of the bilaminar zone of the intra-articular disc (the retrodiscal pad).
How does the tightness of the capsule vary above and below the joint disc?
The capsule is loose above the joint disc and tight below it.
What are the main features of the capsule of the joint?
Envelops the whole joint
Attached above to the articular surface and below to the neck of the condyle
Associated with thick, vascular but loosely arranged connective tissue (retrodiscal pad)
Loose above the joint disc and tight below it
Synovial membrane of TMJ 
It lines the inner surface of fibrous capsule and margins of intra articular disc, but does not cover the articular surfaces of joint
 Secretes synovial fluid
The function of this fluid is to provide
1. a liquid environment for the joint surfaces
2. lubrication to increase efficiency and reduce erosion
3. Synovial fluid also is believed to act as a nutrient fluid for the avascular tissues covering the articular surfaces and for the disk.
Synovial fluid composition
The chemical composition of synovial fluid indicates that it is a dialysate of plasma supplemented with proteins and proteoglycans
Synovial fluid also may contain a small population of varying cell types such as
monocytes, lymphocytes, free synovial cells, and occasionally polymorphonuclear leukocytes
 important components of the fluid are
 Proteoglycans, which aid in lubrication of joint
 Hyaluronan ----increases viscosity & elasticity
 Hyaluronic Acid
 Lubricin
 Collenageses
 Instertitial fluid
What are the ligaments of TMJ
Ligament is a tough fibrous connective tissue band that connects bones
The position and movement of the joint is controlled by ligaments which act as strengtheners and limit excessive movements during muscle movements
Enumerate ligaments of TMJ
Temporomandibular (Lateral) Ligament
 Accessory Ligaments,
 Sphenomandibular Ligament 
 Stylomandibular Ligament
 Pterygomandibular raphe