Download FUNCTIONAL ANATOMY OF TEMPOROMANDIBULAR JOINT

FUNCTIONAL ANATOMY OF
TEMPOROMANDIBULAR JOINT
TEMPOROMANDIBULAR JOINT
Two components :
PASIF COMPONENTS
1.Bone
- Fossa mandibularis ossis temporalis
- Capitulum mandibula ( condyle )
- Tuberculum articulare
( articular eminence )
2.Capsule and ligaments
3.Articular disc
ACTIVE COMPONENTS
Masticator muscles
1. Masseter
2. Temporalis
3. Pterygoideus medialis
4. Pterygoideus lateralis
Additional muscles
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
The TMJ is divided into superior and inferior
cavity by the articular disc
1. Superior cavity
- Superior : fossa mandibula
Inferior : discus articularis
- Gliding action between condyle and
articular eminence
2. Inferior cavity
- Superior : discus articularis
Inferior : condyle
- Hinge action between undersurface of the
disc and the rotating surface of the condyle
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 )
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
- 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
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
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
~ 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
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
* 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
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
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
- 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
- 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
- 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
• 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
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
The synovial fluid serves two purposes :
1. Acts as a medium for providing metabolic
requirement, since the articular surfaces of the
joint are nonvascular
2. As a lubricant during function
Two mechanisms of the lubrication :
1. Boundary lubrication
Prevents friction in the moving joint
2. Weeping lubrication
Eliminates friction in the compressed but not
moving joint
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
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
- 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
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
- 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 :
* 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
*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
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
palatina
- tuber maxillae
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
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 )
• Caput inferior
Origo : - facies lateralis lamina lateralis
processus pterygoideus
extends backward, upward and outward to
insert on the neck of the condyle ( fovea
pterygoidea )
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