1. FUNCTIONAL ANATOMY OF TEMPOROMANDIBULAR JOINT

2. TEMPOROMANDIBULAR JOINT
Two components :
PASIF COMPONENTS
1.Bone Fossa mandibularis ossis temporalis Capitulum mandibula ( condyle )
- Tuberculum articulare
( articular eminence )

3. 2.Capsule and ligaments
3.Articular disc
ACTIVE COMPONENTS
Masticator muscles
Masseter
Temporalis
Pterygoideus medialis
Pterygoideus lateralis
Additional muscles

4. Considered as a ginglymoarthrodial joint :
- hinging movement ~ ginglymoid joint
- gliding movement ~ arthrodial joint
It is formed by mandibular condyle fitting into mandibular fossa and the two bones is separated by articular disc
It is classified as a compound joint ( at least 3 bones ) ~ functionally the articular disc served as a nonossified bone

6. The TMJ is divided into superior and inferior cavity by the articular disc
Superior cavity
- Superior : fossa mandibula
Inferior : discus articularis
- Gliding action between condyle and
articular eminence
Inferior cavity
- Superior : discus articularis
Inferior : condyle
- Hinge action between undersurface of the
disc and the rotating surface of the condyle

8. MANDIBULAR CONDYLE
= Processus condyloideus
It is the posterior portion of the ramus mandibula that extends upward
Mediolateral : 15 – 20 mm
Anteroposterior : 8 – 10 mm
Anterior view : medial and lateral poles,
the medial pole generally more prominent
The actual articulating surface ~ extends
anteriorly and posteriorly to the most superior aspect ( P > A )

10. MANDIBULAR FOSSA
The squamous portion of the temporal bone ( concave )
Anterior : a convex bony prominence
( tubercle ) = articular eminence
Posterior : squamotympanic fissure (M-L)
~ anteromedial : petrosquamous fissure
~ posteromedial : petrotympanic fissure

11. - The posterior roof is thin ~ not designed to sustain heavy force ~ in which condyle situated
The articular eminence consists of thick dense bone ~ to tolerate such forces
- The steepness of the articular eminence surface ~ dictates the pathway of the condyle

13. CAPSULE AND LIGAMENTS
1.Capsula articularis ~ capsular ligament
- It surrounds the entire TMJ
- Superior attachment ~ the borders of the
articular surface of the mandibular fossa
and articular eminence
Inferior attachment ~ collum mandibula
- Function :
~ to resist any medial, lateral or inferior
forces that tend to separate or dislocate the
articular surface
~ to retain the synovial fluid

15. 2.Collateral ( discal ) ligaments
- From medial and lateral borders of the disc to the poles of the condyle
~ the medial discal ligament
~ the lateral discal ligament
- Dividing the joint mediolaterally into superior and inferior joint cavities
- Composed of collagenous connective tissue
- Function :
~ allow the disc move passively with the condyle
as it glides A - P

16. ~ permit the disc to be rotated A-P on
the articular surface of the condyle
These ligaments are responsible for the hinging movement between the condyle and the articular disc
- They have a vascular supply and are innervated

17. 3.Temporomandibular ligament
- It lies at the lateral aspect of the capsular
ligament
- Composed of two parts :
*Outer oblique portion
From the outer surface of the articular
tubercle and zygomatic process postero
inferiorly to the outer surface of the
condylar neck ~ it resists excessive
dropping of the condyle so limiting the
the extent of mouth opening

18. * Inner horizontal portion
From the outer surface of the
articular tubercle and zygomatic
process posteriorly and horizontally
to the lateral pole of the condyle
and posterior part of the articular
disc ~ it limits posterior movement
of the condyle and disc

20. 4.Sphenomandibular ligament
- It is an accesory ligament
- From the spine of the sphenoid bone and
extends downward to lingula mandibula
5.Stylomandibular ligament
- The second accesory ligament
- From the styloid process and extends
downward and forward to the angle and
posterior border of the ramus mandibula
- It limits excessive protrusive movements
of the mandible

22. ARTICULAR DISC
Composed of dense fibrous connective tissue devoid of any blood vessels or nerve fibers
Sagittal plane ~ can be divided into 3 regions according to thickness
- anterior border
- posterior border ~ slightly thicker than
anterior border
- central area is the thinnest ~ intermediate
zone ~ in which condyle is located normally

23. Anterior view ~ the disc is generally thicker
medially than laterally ~ increased space between the condyle and the articular fossa toward the medial of the joint
The precise shape of the disc ~ morphology of the condyle and mandibular fossa
- During movement the disc is somewhat flexible and can adapt to the functional demands of the articular surface ~ do not imply that morphology of the disc is reversibly altered during movement

25. The disc maintain its morphology unless destructive forces or structural changes occurs ~ its morphology can be irreversibly altered ~ biomechanical changes during function
RETRODISCAL TISSUE
The articular disc is attached posteriorly to this region
- It is a loose connective tissue region that highly vascularized and innervated

26. Superior : superior retrodiscal lamina
( contains many elastic fibers ) ~ bilaminary zone
It attaches the disc posteriorly to the tympanic plate
Inferior : inferior retrodiscal lamina
( composed chiefly collagenous fibers )
It attaches the inferior border of the posterior edge of the disc to the posterior margin of the articular surface of the condyle
- The remaining body of the tissue is attached posteriorly to a large venous plexus ~ it fills with blood as the condyle moves forward

27. Anterior region of the disc is attached to the capsular ligament
- Superior : anterior margin of the articular
surface of the temporal bone
Inferior : anterior margin of the articular
surface of the condyle
- Composed of collagenous fibers
Anteriorly the disc is also attached by tendinous fibers to the superior lateral pterygoid muscle

29. The articular surface of the mandibular fossa and condyle are lined with dense fibrous connective tissue ~ affords several advantages over hyaline cartilage :
- less susceptible to the effects of aging
~ less likely to break down over time
- a better ability to repair
The internal surface of the joint cavity are surrounded by specialized endothelial cells that form a synovial lining ~ produces synovial fluid
So TMJ ~ a synovial joint

30. The synovial fluid serves two purposes :
Acts as a medium for providing metabolic requirement, since the articular surfaces of the joint are nonvascular
As a lubricant during function
Two mechanisms of the lubrication :
Boundary lubrication
Prevents friction in the moving joint
Weeping lubrication
Eliminates friction in the compressed but not moving joint

31. MUSCLES OF MASTICATION
MASSETER
Rectangular muscle
There is two portions or heads ( caput )
Superficial head ( Caput superficial )
Origo : - processus zygomaticus ossis
maxillae
- 2/3 ventral of the inferior border of the
zygomatic arch
Insertio : extends downward and backward to the
tuberositas masseterica

32. Profundus head ( Caput profundus )
Origo : - 1/3 dorsal of the inferior border of
the zygomatic arch
- medial surface of the zygomatic
arch
Insertio : extends downward and forward to
ramus mandibula and lateral
surface of processus coronoideus

33. As fibers of the masseter contract ~ mandible is elevated and the teeth are brought into contact
The superficial portion may also aid in protruding the mandible ~ the deep portion stabilize the condyle against articular eminence

35. TEMPORALIS
A fan-shaped muscle
Origo : - temporal fossa
Its fibers extend downward between the zygomatic arch and the lateral surface of the skull
Insertio : - processus coronoideus
- ramus mandibula

36. Contraction of the muscle elevates the mandible and the teeth brought into contact
If only portions contract, the mandible is moved according to the direction of those fibers that are activated
According to fiber direction and ultimate function, it can be divided into 3 distinct areas :

37. * Anterior portion
- The fibers are directed almost vertically
- Contraction ~ mandible is raised
vertically
* Middle portion
- The fibers run obliquely across the lateral
aspect of the skull ( forward as they pass
downward )
- Contraction ~ elevate and retrude the
mandible

38. *Posterior portion
-Run almost horizontally, coming forward above the ear to join other temporalis fibers as they pass under the zygomatic arch
-The function is somewhat controversial ~
causes elevation and only slight retrusion

40. PTERYGOIDEUS MEDIALIS
Consists 2 heads ( caput )
Caput superficial
Origo : - facies medialis lamina lateralis
processus pterygoideus ( fossa
pterygoideus )
- processus pyramidalis ossis
palatina
Caput profundus
Origo : - processus pyramidalis ossis
- tuber maxillae

42. Extend downward, backward and outward to insert along the medial surface of the mandibular angle (tuberositas pterygoidea)
- With the masseter, it forms a muscular sling ~ support the mandible
- Contraction ~ mandible is elevated and the teeth are brought into contact
- It is also active in protruding the mandible
- Unilateral contraction ~ mediotrusive movement of the mandible

44. PTERYGOIDEUS LATERALIS
It consists 2 heads or bellies with different function
Caput superior
Origo : facies infratemporalis ala magna
ossis sphenoidalis,
extending almost horizontally, back
ward and outward to insert on the :
articular capsule, the disc and the
neck of the condyle ( fovea pterygoid )

45. Caput inferior
Origo : - facies lateralis lamina lateralis
processus pterygoideus
extends backward, upward and outward to
insert on the neck of the condyle ( fovea
pterygoidea )

46. Function :
The superior lateral pterygoid is active during power stroke ~ closure mandible against resistance ( chewing and clenching )
While the inferior active during opening, the superior remains inactive, becoming active only in conjunction with the elevator
The right and left inferior contracts simultaneously ~ the condyles are pulled down the articular eminence and the mandible is protruded
The inferior functions with the mandibular depressors ~ the mandible is lowered and the condyles gide forward and downward on the articular eminences