Tmj Flashcards
JOINT CAPSULE
• consists of fibrous tissues that covers or wraps the TMJ • it seals the joint space
JOINT CAPSULE
attached to TMJ by 2 anterior and 2 posterior lamella:
- posterior and superior: squamoustympanic fissure
- anterior and superior: articular eminence
- anterior and inferior condyle
- posterior and inferior condyle
- laterally: glenoid fossa
JOINT CAPSULE
• all lamellas consists of fibrous tissue except superior lamella (fibrous & elastic)
• the connective tissue between the posterior superior and
• the lateral aspect of the capsule is thickened to form a fan-shaped
temporomandibular ligament-restricts the displacement of the mandible
SYNOVIAL MEMBRANE
▪ the capsule is lined on its inner surface by synovial membrane
▪ secretes the synovial fluid that occupies the joint cavities
▪ the membrane consists of folds and villi which protrude into the joint
cavity. • the folds increases with age and are more prominent in joints
affected by pathological conditions
SYNOVIAL MEMBRANE
▪ Consists of 2 layers:
Cellular intima
Vascular subintima
Cellular intima
Consists of synovial cells
embedded in an amorphous, fiber-free intercellular matrix.
Vascular subintima
Loose connective tissue
containing vascular elements and scattered with cells such as fibroblasts, macrophages, mast cells, fat cells.
cells in vascular subintima consists some elastic fibers which prevent folding of the membrane
Type A(Macrophage like) cells Type B(Fibroblast like) cells
Type A(Macrophage like) cells
• exhibit phagocytic properties.
• cytoplasm of cells contains mitochondria,
lysosomal elements and Golgi complex.
Type B(Fibroblast like) cells
• synthesize hyaluronate found in the
synovialfluid.
• cells contain many rough endoplasmic
reticulum
FUNCTIONS OF SYNOVIAL FLUID
• provides a liquid environment for the joint
surfaces
• lubrication to increase efficiency of joint
movement and reduce erosion/.
• nutrition to articular surfaces and disk.
Histology of the articulating surface
The articulating surface of both the temporal bone and condyle consistsof:
Fibrous layer
Proliferative zone
Proliferative zone
contains chrondoblasts associated with the
formation ofcartilage
Chondroblasts forms the extracellular matrix of proteoglycans
and type II collagen and these cells may become entrapped in the
matrix as chondrocytes. With age, the proliferative activity of the
cells ceases. The cartilage is converted to fibrocartilage and
eventually the cartilage is mineralized.
• The proliferative layer can resume their proliferative activity
when the occasion demands.
Fibrous layer
dense, largely avascular layer of type I collagen (thicker at
the articular eminence)
In child’s condyle:
• the proliferative zone is large
• presence of hypertrophic chondrocytes
(cartilage forming cells) - the zone where
endochondral ossification occurs).
Blood supply
Branches of external carotid artery (superficial temporal, deep auricular, anterior tympanic and ascending pharyngeal arteries).
BIOMECHANICS OF TMJ
The muscles act on the TMJ to provide stability and to allow the following movements:
Rotatory, Translatory movement
Translatory movement
• opening of the mandible more than 2.5 cm • involves translation of the condyle to the
articular eminence
Rotatory
• opening of the mandible less than 2.5 cm
• involves rotation of the condyle in the glenoid
fossa (pure hinge movement)
ENVELOPE OF MOTION:
Contact points between the incisors during opening and closing of jaws Refers to the space within which all movements of the mandible occurs Limited by TMJ ligaments
Envelope of motion:
Consists of two phase:
Opening of less than 2.5 cm involves rotation of the condyle in the glenoid fossa (pure hinge movement)
Opening of more than 2.5 cm involves translation of the condyle to the articular eminence
SUBLUXATION
An incomplete dislocation of the condyle with
maximum opening
the condyle translates anterior to the articular
eminence and is able to return to the fossa
after either self manipulation or spontaneous
voluntary retention.
It usually report a momentarily / short duration
of open dislocation with the jaw ‘sticking’ /
temporarily inability to close the jaw
completely.
