MUSCLES OF MUSCLES OF MASTICATIONMASTICATION

Dr. GURUDASAN,Dr. GURUDASAN,

DEPARTMENT OF ANATOMY,DEPARTMENT OF ANATOMY,

MALABAR MEDICAL COLLEGE,MALABAR MEDICAL COLLEGE,

CALICUT.CALICUT.

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OBJECTIVESOBJECTIVES

At the end of the lecture, a student should knowBoundaries of temporal and

infratemporal region and the structures present in it.

The attachments of the muscles and their actions, nerve supply and clinical aspects.

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TEMPORAL REGIONTEMPORAL REGION

It is situated on either side of the head above and infront of the auricle.

BOUNDARIES: Above: superior

temporal line Infront: frontal process

of zygomatic arch.The temporal fossa

which forms the floor of the region communicates

below with infratemporal fossa. 325-01-2014

Superior temporal line

Frontal process of Zygomatic arch

Temporal fossa

CONTENTS OF TEMPORAL REGIONCONTENTS OF TEMPORAL REGION

Temporalis muscle and its covering fascia (Temporal fascia)

Deep temporal nerve and vessel

Auriculo-temporal nerve

Superficial temporal vessels

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INFRATEMPORAL REGIONINFRATEMPORAL REGIONIt is situated below

the middle cranial fossa of the skull as a continuation of temporal fossa.

BOUNDARIES: Ant: Body of the

maxilla Post: Styloid process Med: Lateral pterygoid

plate Lat: Ramus of mandible

and its coronoid process

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Maxilla

Lat. Pterygoid plate

Styloid process

Boundaries (contd....)Boundaries (contd....)

Above: Infratemporal surface of greater wing of sphenoid

Below: the fossa is open and continuous with the tissue spaces of pharynx and oesophagus.

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Infratemporal Surface of greater wing Of sphenoid

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CONTENTS – INFRATEMPORAL CONTENTS – INFRATEMPORAL FOSSAFOSSA

Lateral and medial pterygoid muscles and insertion of temporalis

Mandibular nerve and its branches

Maxillary artery and its branches

Pterygoid venous plexus & maxillary vein

Otic ganglion, chorda tympani nerve

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MUSCLES OF MASTICATIONMUSCLES OF MASTICATIONIntroduction:They are

i) Temporalisii) Masseteriii) Medial pterygoidiv) Lateral pterygoid

Are derived from I pharyngeal arch.

Are supplied by branches of mandibular nerve ( I arch nerve).

Temporalis

Masseter

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Act on the tempero-mandibular joint and moves mandible. Are principally anti-gravity muscles (except Lateral pterygoid)

Lateral pterygoid

Medial Pterygoid

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Lateral Pterygoid

Medial Pterygoid

Deep muscles of Mastication – Posterior view

Trunk of Mandibular Nerve

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GENERAL FEATURESGENERAL FEATURES All the muscles arise from cranium and

insert in the mandible. All the muscles develop from the

mesoderm of I pharyngeal arch.All the muscles are supplied by nerve of

I pharyngeal arch (Mandibular nerve).All the muscles act against the gravity

(anti-gravity) except lateral pterygoid.Buccinator is considered as the

accessory muscle of mastication.

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Muscles in detail....Muscles in detail....I) Temporalis: Its 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

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TEMPORAL FASCIA

Attachment:

Above: Superior temporalline

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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II) Masseter: It is quadrilateral in Shape. Can be palpated in living subjects on

clenching the teeth It consists of 2 layers

viz. 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 mandibleSuperficial fibres: Protracts the mandible

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Masseter - Relations Masseter - Relations Superficial:Parotid gland & its

duct, branches of facial nerve,

Transverse facial branches of superficial temporal artery.

Deep: Temporalis and ramus of

mandible, buccinator and buccal pad of fat

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Masseter

Parotid gland and its duct

Transverse facial br

Buccinator

Pterygoid musclesPterygoid musclesThere 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 ptergoid Lateral ptergoid 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 insertSome fibres of upper head may insert in the capsule of tempero-mandibular jointin the capsule of tempero-mandibular joint

Upper head

Lower head

Capsule of TMJ

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Lat. Pterygoid - Lat. Pterygoid - AttachmentAttachment

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

Relations – Lateral Relations – Lateral pterygoidpterygoid

Superficial:Masseter, ramus

of mandible, temporalis, maxillary artery.

2225-01-2014Ramus of mandible

Masseter

Maxillary artery

Temporalis

Lat.Pterygoid

Relations – Lateral Relations – Lateral pterygoidpterygoidDeep:

Mandibular nerve and its branches

Chorda tympani nerve Medial pterygoid muscle Middle meningeal artery Spheno-mandibular

ligament Upper border – Deep

temporal and masseteric nerve emerge.

Lower border: Lingual nerve, inferior alveolar nerve.

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Middle meningeal artery

Chorda tympani N

Lingual N

Inf.Alveolar N

Med.Pterygoid

Maxillary artery and buccal br. Of mandibularNerve passes between two heads

Owing to its relations, lateral pterygoid is called key muscle of infratemporal regionOwing to its relations, lateral pterygoid is called key muscle of infratemporal region

Trunk of mandibular nerve

Deep temporal nerves

Masseteric Nerve

Medial pterygoidMedial 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

Clinical AnatomyClinical Anatomy

Trismus: Tonic spasm of both masseters is the characteristic symptom of tetanus which produces “lock jaw”

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Clinical Anatomy Clinical Anatomy (contd...)(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 Clinical Anatomy (contd...)(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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THANK YOUTHANK YOU

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