Download - Muscles of Mastication
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MUSCLES OF MASTICATION
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CONTENTS Introduction Embryological development Masticator space Origin, Course, Insertion, Relation – Muscles
of Mastication Fascia- Masseteric, Temporalis, Pterygoid Mandibular sling Buccinator Muscle Nerve supply Blood supply Actions & Group actions Applied Anatomy Conclusion References
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EMBRYOLOGICAL DEVELOPEMENT
• Mesoderm of the 1st Branchial Arch
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MASTICATOR SPACE(PARVIZ)
CONTENTS4 Muscles of MasticationRamus & Posterior portion of body of
MandibleFascia – Masseteric , Pterygoid, Temporalis
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MASSETER
Quadrilateral / Rectangular
Covers lateral surface of Ramus of mandible
3 superimposed layers, that blend anteriorly. (PARVIZ JANFAZA)
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ORIGIN,
• MOST ANTERIOR FIBRES arises as a thick aponeurosis = Maxillary pocess of zygomatic
bone(GRAYS) • SUPERFICIAL (largest) = anterior 2/3 lower border, Zygomatic Arch
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ORIGIN,
• MIDDLE
= anterior 2/3 posterior 1/3 deep surface & lower border zygomatic arch
• DEEP = posterior 1/3 deep surface zygomatic arch
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Course of masseter
• Superficial layer – passes downwards& backwards at an angle of 45 degree
• Middle & Deep Layer – pass vertically downwards
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INSERTION,
• SUPERFICIAL, = posterior lower ½, lateral surface, Ramus & angle of mandible• MIDDLE = central part, lateral, Ramus
• DEEP = upper ½ , lateral, Ramus & lateral surface,Coronoid Process
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• Middle & Deep layers together constitute the deep part of the masseter,
refd to in the NOMINA ANATOMICA ( MacDougall ,1955 ); they form a cruciate muscle (GRAYS)
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RELATIONS,
• SUPERFICIAL - Skin - Platysma - Risorius - Zygomatic Major - Antr part,Parotid Gland - Parotid duct - Facial n, terminal brs - Transverse Facial vessels
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• DEEP - Ramus - Lower part of Temporalis - Massetric n & a , reach the deep surface of m. by
passing through the Dorsal part of Mandibular Incisure
• ANTERIORLY - Buccinator - Buccal n• POSTERIORLY – Parotid gland
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PAROTID MASSETERIC FASCIA
• Covers Masseter (except,as its deep upper portion. Here there is a communication with fascial planes associated with the insertion of temporalis m.) &splits to invest ParotidGland
• Attaches, Zygomatic arch
Lower border of Mandible
Continues, Investing Cervical Fascia over Sternocleidomastoid m,
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Extends deep & fuses with, Fascia Extends deep & fuses with, Fascia of Posterior Belly of Digastric m. of Posterior Belly of Digastric m. as Stylomandibular ligament.as Stylomandibular ligament.
Encircles, anteriorly- Ramus Encircles, anteriorly- Ramus deep- Medial Pterygoid deep- Medial Pterygoid m.m.
Fuses with, dense&tough Fuses with, dense&tough superficial fascia covering parotid superficial fascia covering parotid gland. Irregular septa into the gland. Irregular septa into the gland.gland.
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TEMPORALIS
• Fan shaped
• Fills Temporal Fossa
ORIGIN, Bones forming Temporal fossa (excluding
zygomatic bone) Temporal Fascia (deep surface)
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Course,
• Antr fibres- vertically downwards • Postr fibres – horizontally forwards• Intermediate – obliquely
-------- converge to form a tendon (TEMPORALIS TENDON) &
pass thr gap b/w Zygomatic arch and side of the skull
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INSERTION,
Coronoid Process, = deep (medial) surface + = margins (apex, anterior & posterior
border)
Ramus, anteromedial aspect, nearly to the
last molar tooth
(GOSLING)
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RELATIONS,
• SUPERFICIAL -Skin -Auricularis anterior -Auricularis superior -Temporal branch-Facial n -Zygomatico temporal nerve -Superficial temporal a & v -Galea aponeurotica -Zygomatic arch -Masseter m
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• DEEP,
-Temporalis fossa
-Lateral pterygoid m
-Superficial head, medial pterygoid m
-Buccinator m
-Maxillary artery
-Deep temporalis n
-Buccal vessels & n
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TEMPORAL FASCIA The most cranial extension of the Deep Cervical
Fascia Thick Fibrous Aponeurotic sheets, covers
Temporalis
Supr, single layered
Superior Temporal Line Infr, splits into 2 layers
inner&upper lips, upper bor, Zygo arch. Gap b/w 2, - Zygomatic br.of Superficial Temporal a.
- Zygomaticotemporal n. Continues, Masseteric Fascia
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Relations, Temporal Fascia SUPERFICIAL- 1.Skin 2.Auricularis Anterior Auricularis Superior (gives origin to) 3.Superficial Temporal a & v 4.Auriculo-temporal N 5.Facial N – temporal br 6.Galea Aponeurotica (Epicranial Aponeurosis) DEEP – (gives origin to) superficial fibers of Temporalis
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LATERAL PTERYGOID
• 2 heads – upper, small _ lower, large
ORIGIN UPPER HEAD. = Infratemporal surface = Infratemporal crest of Greater Wing of Sphenoid LOWER HEAD = Lateral surface of Lateral Pterygoid Plate
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Course,
• Both heads converge &
run Backwards_laterally
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INSERTION,
Pterygoid Fovea (a depression),
on Anterior surface, Neck of
mandible Anterior margin of,
Articular disc &
Capsule of TMJ
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INSERTION,
Pterygoid Fovea (a depression),
on Anterior surface, Neck of
mandible Anterior margin of,
Articular disc &
Capsule of TMJ
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Relations
key muscle of the region,because its relations provide a fair idea about the layout of structure in Infratemporal Fossa
SUPERFICIAL 1.Ramus 2.Maxillary a 3.Tendon of temporalis 4.Masseter
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• 1.Deep head of Medial Pterygoid m.
• 2.Sphenomandibular Ligament
• 3.Middle Meningeal a
• 4.Mandibular n
DEEPDEEP
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STRUCTURES EMERGING AT THE UPPER BORDER
1.Masseteric n
2.Deep Temporal n
STRUCTURES EMERGING AT THE LOWER BORDERSTRUCTURES EMERGING AT THE LOWER BORDER 1.Lingual n1.Lingual n 2.Infr.Alveolar n2.Infr.Alveolar n 3.Middle Meningeal a3.Middle Meningeal aSTRUCTURES PASSING THROUGH THE GAP STRUCTURES PASSING THROUGH THE GAP BETWEEN 2 HEADSBETWEEN 2 HEADS 1.Maxillary a 1.Maxillary a 2.Mandibular n, Buccal br 2.Mandibular n, Buccal br
Pterygoid Plexus Of Veins Surround The Lateral Pterygoid Plexus Of Veins Surround The Lateral PterygoidPterygoid
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MEDIAL PTERYGOID
• Quadrilateral Muscle
• 2 heads – Superficial, small
Deep, large
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ORIGIN
• Superficial
- Tuberosity of Maxilla
- Grooved surface (Lateral aspect)of Pyramidal process,Palatine bone
• Deep - Medial surface,Lateral Pterygoid Plate
- adjoining part of Pyramidal process,Palatine Bone
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course
• Incline obliquely,
run Downwards_Backwards_Laterally
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INSERTION
as a strong tendinous lamina,
Roughened area on the Medial surface of
Angle adjoining part of Ramus
below – Mandibular Foramen
behind – Mylohyoid Groove
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RELATIONS
SUPERFICIAL (upper part)- seperates Lateral Pterygoid
Lateral Pterygoid Plate Lingual Nerve
Inf.Alveolar Nerve Superficial (lower part) –seperates Ramus Lingual Nerve Inf. Alveolar Nerve Maxillary Artery Sphenomandibular Ligament
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DEEP Superior Constrictor- anteriorly,tendinous band i.e. Pterygomandibular Raphe
crossed by, Styloglossus m Stylopharyngeus m Stylohyoid ligament Glossopharyngeal n.Gap b/w upper border of superior constrictor & base of skull Tensor palati Levator palatiAnterior to Tensor palati, Medial Pterygoid plate (I. Singh)
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PTERYGOID FASCIA
• Encases both Pterygoid muscles and attaches to the Stylomandibular Ligament
• Between the sphenoid spine and the lingula of the mandible facial condensation to form the sphenomandibular ligament
• The terminal part of this facia between the sphenoid spine and the posterior margin of the lateral pterygoid muscle is called the pterygospinous ligament
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MANDIBULAR SLING
• Mac Conaill (1975) – the most superficial fibres of masseter are continuous at the lower border of the mandible with the attachment of the medial pterygoid m.
• The attachments of the medial pterygoid & the masseter muscle provide a muscular sling that suspends the angle of the of the jaw.
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• They provide a functional articulation b/w the maxilla & mandible,with the TMJ acting as a guide
• When the jaw opens or closes, the mandible moves along a center of rotation created by the attachment of the sling & the sphenomandibular ligament
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Buccinator muscle
• Which assists in chewing by helping ( to keep food b/w upper & lower teeth) & (away from the cheeks)
• Is not classified as Muscle of Mastication as it does not move the mand
(Mc Minns )
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MOTOR NERVE INNERVATIONS,5TH Cranial Nerve, Mandibular br.
Masseter- -Masseteric NTemporalis- -Antr & Postr Deep
Temporal N
Lat.Pterygoid -N to Lat.PterygoidMed.Pterygoid- N to Med. pterygoid
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Blood Supply
MAXILLARY ARTERY (second part)
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ACTION, MASSETER
Elevation Protrusion / Protraction
( by, Anterior fibres )
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ACTION, TEMPORALIS
Elevation
Retraction
( by, Posterior horizontal fibres )
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ACTION, LATERAL PTERYGOID
• Depression
• Protrusion
• Side to Side Movement
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ACTION, MEDIAL PTERYGOID
• Elevation
• Protrusion
• Side to Side Movement
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ACCESSORY MUSCLES OF
MASTICATION Digastric
Geniohyoid
Mylohyoid
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Biomechanics of the
MASTICATORY SYSTEM
( Hannam )
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Applied Anatomy_ Surgical Implications