tmj and muscles of mastication dr rania gabr. objectives identify the parts of the mandible. know...
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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 SURFACES- A. 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
• Elevation• Depression• Retraction• Protraction• Side to side
• 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.
Movements
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
TemporalisIts a fan shaped muscleCovered by temporal fasciaOrigin: 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 14
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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
ACTION: ANT - Elevation of the mandiblePOST – Retraction of mandible
Anterior fibres – vertical
Middle fibres - Oblique
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 archInsertion: 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 mandibleSuperficial 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
Medial pterygoidBuccinator
Partotid duct
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Lateral pterygoid It is a short, thick muscle
consisting of two partsI) Upper headII) 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)
Some fibres of upper head may insert in the capsule of tempero-mandibular joint
Upper head
Lower head
Capsule of TMJ
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Lat. Pterygoid - Attachment
Infra temporal Sufrace of greater wing of sphenoid
Lateral surface of lateral pterygoid plate
Upper head
Lower head
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Action: opening of mouth (Depression of mandible) by pulling forward the head of mandible. Upper head – chewing, Lower head – protrusion.
Side to side movements: combined action of medial and lateral pterygoid
Nerve supply: Anterior division of mandibular nerve
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
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Superficial head
Deep head
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Action: Elevation of mandible. Together with lateral pterygoid, it helps in side to side chewing movement.
Superficialfibres
Deep fibres
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 AnatomyTrismus:
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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