Transcript TMJ and Muscles of Mastication

TMJ and Muscles of Mastication
Dr Rania Gabr
Objectives
• Identify the parts of the mandible.
• Know the type and formation of temporomandibular
joint.
• Understand the attachment of the capsule and
ligaments of the temporomandibular joint.
• Explain the mechanism of movements taking place at
temporomandibular joint.
• Define the stability factors of the joint.
• Explain the muscles of mastication with their origin,
insertion, nerve supply and actions.
• Discuss maxillary artery.
Gross Anatomy
This is a synovial joint of condylar
variety.
COMPONENTS:
• Mandibular condyles
• Articular surfaces of Temporal
bone
• Capsule
• Articular disc
• Ligaments
• ARTICULAR SURFACESA. Upper part a) Articular eminence,
b) ant. part of mandibular
fossa.
B. Inferior surface head of the mandible.
ARTICULAR DISC
(MENISCUS)
• Fibro cartilaginous tissues
• Disc divides the compartment
into 2:
• Upper formed by Temporal bone
and articular disc (Menisco
temporal)
• Lower formed by mandible and
articular disc (Menisco
mandibular)
CAPSULE
• Fibrous membrane that
surrounds the joint
• Covers the joint from all
around
• Thin above the disc and thick
below it
• Encloses the disc
• Attaches above: to the
margins of the mandibular
fossa
• Attaches below: to the neck
of the mandible
• The inner aspect of capsule
attaches to disc
– Above disc – capsule loose
– Below disc - tight
LIGAMENTS
 Major Ligaments
 Temporomandibular
ligament
 Lateral ligament
 Minor Ligaments
 Stylo mandibular ligament
 Spheno mandibular
ligament
Movements
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•
•
•
•
Elevation
Depression
Retraction
Protraction
Side to side
Movements
• Side to side – grinding movements
– Mandible is alternately protracted and retracted with the two
sides moving in opposite directions so that one side is
protracted while the other is retracted
– Actions combined with elevation and depression, rhythmically
and alternately.
– Opening of the jaw (depression) ,is primarily passive or gravity
assisted.
MUSCLES
• Messeter
• Temporalis
• Medial pterygoid
• Lateral pterygoid
INNERVATION
• TRIGEMINAL NERVE:
Mandibular div.
• SENSORY
– Auriculo temporal nerve:
from the posterior
division of the
mandibular nerve
– Messeteric nerve: from
the anterior division of
the mandibular nerve
• MOTOR
– Mandibular division of
trigeminal nerve
Temporalis
Its a fan shaped muscle
Covered by temporal fascia
Origin: Medial wall of the
temporal fossa and
temporal fascia
Insertion: Anterior margin
of coronoid process and
anterior border of the
ramus of mandible
Nerve supply: Deep
temporal branch of
anterior division of
mandibular nerve
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TEMPORAL FASCIA
Attachment:
Above:
Superior temporal line
Below:
It splits into 2 layers and
insert into respective borders
of zygomatic bone
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ACTION:
ANT - Elevation of the
mandible
POST – Retraction of mandible
Middle fibres - Oblique
Anterior fibres – vertical
Posterior fibres - Horizontal
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Masseter
It is quadrilateral in shape.
 Can be palpated in living
subjects on clenching the teeth
 It consists of 2 layers :
Superficial and deep.
Origin:
Lower margin and deep aspect of
zygomatic arch
Insertion:
Lateral surface of ramus and
coronoid process of mandible
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Nerve supply:
Masseteric nerve from
the anterior division of
mandibular nerve.
Action:
Elevates the
mandible
Superficial fibres:
Protracts the
mandible
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Pterygoid muscles
• There are medial and
lateral pterygoid
muscles.
• They extend from the
pterygoid plates and
insert in the mandible.
Lateral pterygoid
Partotid duct
Buccinator
Medial pterygoid
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Lateral pterygoid
 It is a short, thick muscle
consisting of two parts
I) Upper head
II) Lower head
Origin:
Upper head: Infratemporal
surface of greater wing of
sphenoid
Lower head: Lateral surface of the
lateral pterygoid plate
Insertion: Pterygoid fovea
(depression on the front of the
neck of the mandible)
Capsule of TMJ
Upper head
Lower head
Some fibres of upper head may insert
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in the capsule of tempero-mandibular joint
Lat. Pterygoid - Attachment
Infra temporal
Sufrace of greater
wing of sphenoid
Upper head
Lower head
Lateral surface of
lateral pterygoid plate
Nerve supply: Anterior division of
mandibular nerve
Action: opening of mouth (Depression of mandible) by pulling forward the
head of mandible. Upper head – chewing, Lower head – protrusion.
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Side to side movements: combined action of medial and lateral pterygoid
Medial pterygoid
• It consists of large deep head
and small superficial head.
 Origin:
 Deep head: Arises from the
medial surface of lat.pterygoid
plate
 Superficial head:
Tuberosity of maxilla
 Insertion:
Medial surface of ramus and
angle of mandible.
Nerve supply: Branch from the
trunk of mandibular nerve
Deep head
Superficial head
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Deep fibres
Superficial
fibres
Action: Elevation of mandible. Together with lateral pterygoid,
it helps in side to side chewing movement.
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VASCULARISATION
• Branches of External Carotid
Artery
– Superficial temporal
artery
– Deep auricular artery
– Anterior tympanic artery
– Ascending pharyngeal
artery
– Maxillary artery
VASCULARISATION
• The Blood supply to
TMJ is only Superficial,
i.e there is no blood
supply inside the
capsule
• TMJ takes its
nourishment from
Synovial fluid
Clinical Anatomy
Trismus:
Tonic spasm of both
masseters is the characteristic
symptom of tetanus which
produces “lock jaw”
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Clinical Anatomy (contd...)
 Submasseteric space
infection:
Infection around 3rd
molar tooth may seep
into the space between
the attachment of
masseter with mandible
which leads to visible
swelling and limitation
of jaw movements
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Clinical Anatomy (contd...)
Paralysis of lateral
pterygoid muscles
causes the jaw to
deviate towards the
paralysed side on
opening the mouth as
a result of action of
normal muscle.
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