"Temporomandibular joint forms the
craniomandibular articulation"
· Two synovial joints (right and left) connected with a single
bone “the Mandible” makes the joint unique. Further coordinated movements of
both joints facilitates the mandibular movements.
·
Boney components
1. Contyle of mandible
2. Squamous temporal bone of
the skull
·
TMJ is a Complex joint – by function and by structure
·
Also it is a “Ginglymoarthoridal” jt
Hinging movement – Ginglymoid movement
Gliding
movement – Arthroidal movement
·
Another classification of joints classify TMJ as a Compound
Jt
-
By definition compound jt is joint composed of 3 or more
bones
- TMJ is composed of 2 bones , but considered compound jt because articular discis is considered
functionally non ossified bone
- TMJ differs from other diarthoidal joints of the body
I. TMJ forms bilateral diarthrosis – functioning both Lt Rt joints together
II.Articular surfaces are covered by fibrocartilage instend of
hyaline cartilage
III.TMJ is the only joint which has argitend point of closure,
because when the mouth is closed the teeth come into occlusal contact
The Disc
·
Dense fibrous tissue
·
Devoid of blood vessels and
nerves. Therefore it does not manifest marked inflammation in trauma.
·
Four Regions
1.
Anterior
2.
Intermediated – sits along
articular eminence
3.
Posterior – Thickest – 12 ‘o
clock on contyle
4.
Bilaminar region (Contains
Blood vessels)
Collagen type I – Mainly
1.
Superficial layers – Parallel
to anterior-posterior direction
2.
Central – Oriented random fashion
This arrangement provide
ability with stand forces
 |
| Structure of Temporomandibluar joint |
Anteriorly Disc divides into two lamellae
1.
Superior Lamella – Fuse with
capsule the periosteum of the anterior
slope of articular eminence
2.
Inferior Lamella – anterior
surface of the neck of the condyle
3.
Mid – with fibers of lateral
pterygoid muscle
Muscles of Mastication
Although they are called muscles of
mastication, they always function with other groups of the face, tongue, soft
palate & hyoid bone
Masseter
Superficial
Part
Arises from lower
border of Zygomatic arch
Fibers directed
downward back wards
Insert along the
angle of the mandible
Insertion-
Lower 1/3 of the posterior border of the ramus and along lower boarder
of the mandible to the 8 tooth
Deep Part
Inserts above superficial masseter along the ramus of the mandible -
Function
1.
Elevation of the mandible
Nerve Supple
V Nerve > Mandibular
branch > Masseteric
Nerve
Temporalis
-
Fan shaped muscle
-
Attachment of large muscle
extend to
I.
Small portion of parietal bon- extends
above
II.
Greater Portion of the savamous
portion of the temporal bone
III.
Temporal surface of the frontal
bove
IV.
Temporal surface of greater
wing of the sphenoid bove
·
Temporal Fascia attaches to
supra temporal in border of the zygomatic arch.
·
Temporal Fascia
o
Thickens When passing
downwards.
o
Splits in to two layers.
o
Superficial layer blends
periosteum of the lateral Surface of the Zygomatic arch.
o
Deep Portion blunts T medial
Surface.
o
Many of the muscle fibers
original from the medial surface of the temporal fascia.
·
Insertion of temporalis.
o
Coronoid Process
o
Antero medial Surface of the
ramus of the mandible.
·
Function
o
Elevates the mandible.
·
Innervation
o
Deep temporal branches arising
from the mandibular division of V
Medial Pterygoid
2.
Heads
- Superficial Head
- Deep head
Deep head- Originates from medial Surface
of lateral Pterygoid plate a Pyarmydal Process of the Palatine bone.
Inserted in to Roughened medial Surface of the mandible near the angle of the
mandible.
Superficial Head-Originals from Tuberosity
of the maxilla adjacent Pyramidal process of the Palatine bone.
Joins with deep head to in sear in to
mandible.
Runs-
Downwards
- Backwards
- Laterally
Innervated by – Nerve to medial Pterygoid.
_ Branch of the mandibular.
_ Division of the Trigeminal Nerve.
Lateral Pterygoid
Two heads
·
Superior head
·
Inferior head
v Superior head – Originals from infra temporal
Surface of the grater wing of sphenoid.
Runs backwards, laterally, almost horizontally and
insert to the disk capsule of the TMJ the condyle.
Function – Stabilizer the mandibular condyle against the reticular
eminence during mastication.
v Inferior head - Originals from lateral
Surface of lateral Pterygoid plate.
Fibers extend Back wads, Upwads Out wads to
insert in to neck of the condyle.
Function
Protrusion
Lateral excursion
Innervation
Branch of buccal nerve- From mandible division
of V
Other muscles
1.
Digastrics
2.
Mylohyoid
3.
Geniohyoid
4.
Platysma
