Muscles of mastication

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MUSCLES OF MASTICATION

Medicoapps Masterclass on Muscles of Mastication


 

Don’t Forget to Solve all the previous Year Question asked on MUSCLES OF MASTICATION

MUSCLES OF MASTICATION

INTRODUCTION:

  • Mastication- four muscles of mastication (or musculi masticatorii) – adduction and lateral motion of the jaw.
  • Muscles associated hyoid  also responsible for opening the jaw
  • Embryological origin from the first pharyngeal arch.

TYPES:

  • PRIMARY MUSCLES OF MASTICATION:
  1. Temporalis: fan shaped & fills the temporal fossa.
  2. Masseter (quadrilateral): Covers lateral surface of ramus of Mandible & has 3 layers.
  3. Lateral Pterygoid: Short, conical & has upper 7 lower head.
  4. Medial Pterygoid (quadrilateral):Has a small superficial & a large deep head.

    

MUSCLE ORIGIN FIBERS  INSERTION NERVE SUPPLY & NUCLEI ACTION

Masseter
  1. superficial layer:Ant. 2/3rd of lower border of zygomatic arch & zygomatic process of maxilla
  2. Middle layer: Ant. 2/3rd of deep surface & post. 1/3rd of lower border of zygomatic arch
  3. deep layer:Deep surface of zygomatic arch
  1. superficial:down & back at 45o
  2. Middle & deep:vertically down
  3. 3 layers seperated by an artery & a nerve
  1. Superficial:Lower part of lateral surface of ramus
  2. Middle: middle part of ramus
  3. Deep:Upper part of ramus & coronoid process 

 Massetric nerve(C.N.V3 ant. div.)

(mesencephalic nucleus and the motor nucleus of trigeminal nerve )

  Elevtaes mandible to close mouth
 Temporalis
  1. Temporal fossa excluding zygomatic bone
  2. Temporal fascia 
 Converge & pass through gap deep to zygomatic arch
  1. Margins & deep surface of coronoid process
  2. Ant. border of ramus
  2 deep temporal branches(C.N.V3 ant. div.)
  1. Elevates mandible
  2. Retracts Mandible
  3. Side to side grinding movement

 
 Lateral Pterygoid
  1. Upper Head:Infratemporal surface& greater wing of sphenoid
  2. Lower Head:Lateral surface of lateral pterygoid plate

 

  Back & Lateral & converge for  insertion
  1. Upper head:Pterygoid fovea at neck of mandible
  2. Lower head:Ant. margin of articular disc & TMJ capsule
  Lateral pterygoid branch (Ant. div. of C.N.V3)
  1. Depress mandible
  2. Protrude mandible
  3. grinding movement
 Medial Pterygoid
  1. Superficial Head: Tuberosity of maxilla & adjoining bone
  2. Deep Head:Medial surface of lateral pterygoid plate& adjoining process of palatine bone
  Down, back & laterally  Roughened area on medial surface of angle & adjoinig ramus of mandible, below & behind madibular foramen & mylohyoid groove  Nerve to Medial Pterygoid( Main trunk of C.N. V3)
  1. Elevates Mandible
  2. Protude mandible
  3. Grinding movement
  • SECONDARY MUSCLES OF MASTICATION: 
  • Suprahyoid muscles  
  1. Digastric:    Elevate hyoid , depress mandible
  2. Stylohyoid:  draw the hyoid bone backwards and elevate the tongue.
  3. Mylohyoid:   Raises oral cavity floor, elevates hyoid, elevates tongue, depresses mandible
  4. Geniohyoid: carry hyoid bone and the tongue upward during deglutition
  • Infrahyoid muscles
  1. Sternohyoid: Depress Hyoid bone
  2. Thyrohyoid:  Elevates thyroid Depress Hyoid bone
  3. Omohyoid:    Depresses the larynx and hyoid bone. Also carries hyoid bone backward and to the side
Exam Question
 
  • The muscles of mastication are temporalis, masseter, medial pterygoid, lateral pterygoid
  • Masseter originates from mesencephalic nucleus and the motor nucleus of trigeminal nerve 
  • All primary muscles of mastication are supplied by mandibular nerve 
  • Muscles that elevates mandible to close the mouth are temporalis, masseter & medial pterygoid
  • The only primary muscle that depress mandible to open mouth is lateral pterygoid
  • All Muscles of mastication are supplied by branches from Ant. div. of mandibular branch of TRIGEMINAL NERVE exceptMedial Pterygoid.
 

TYPES:

  • PRIMARY MUSCLES OF MASTICATION:
  1. Temporalis: fan shaped & fills the temporal fossa
  2. Masseter( quadrilateral): Covers lateral surface of ramus of Mandible & has 3 layers
  3. Lateral Pterygoid: Short, conical & has upper 7 lower head
  4. Medial pterygoid (quadrilateral):Has a small superficial & a large deep head

    

MUSCLE  ORIGIN FIBERS  INSERTION NERVE SUPPLY & NUCLEI ACTION

Masseter
  1. superficial layer:Ant. 2/3rd of lower border of zygomatic arch & zygomatic process of maxilla
  2. Middle layer: Ant. 2/3rd of deep surface & post. 1/3rd of lower border of zygomatic arch
  3. deep layer:Deep surface of zygomatic arch
  1. superficial:down & back at 45o
  2. Middle & deep:vertically down
  3. 3 layers seperated by an artery & a nerve
  1. Superficial:Lower part of lateral surface of ramus
  2. Middle: middle part of ramus
  3. Deep:Upper part of ramus & coronoid process 

 Massetric nerve(C.N.V3 ant. div.)

(mesencephalic nucleus and the motor nucleus of trigeminal nerve )

  Elevtaes mandible to close mouth
 Temporalis
  1. Temporal fossa excluding zygomatic bone
  2. Temporal fascia 
 Converge & pass through gap deep to zygomatic arch
  1. Margins & deep surface of coronoid process
  2. Ant. border of ramus
  2 deep temporal branches(C.N.V3 ant. div.)
  1. Elevates mandible
  2. Retracts Mandible
  3. Side to side grinding movement

 
 Lateral Pterygoid
  1. Upper Head:Infratemporal surface& greater wing of sphenoid
  2. Lower Head:Lateral surface of lateral pterygoid plate

 

  Back & Lateral & converge for  insertion
  1. Upper head:Pterygoid fovea at neck of mandible
  2. Lower head:Ant. margin of articular disc & TMJ capsule
  Lateral pterygoid branch (Ant. div. of C.N.V3)
  1. Depress mandible
  2. Protrude mandible
  3. grinding movement
 Medial Pterygoid
  1. Superficial Head: Tuberosity of maxilla & adjoining bone
  2. Deep Head:Medial surface of lateral pterygoid plate& adjoining process of palatine bone
  Down, back & laterally  Roughened area on medial surface of angle & adjoinig ramus of mandible, below & behind madibular foramen & mylohyoid groove  Nerve to Medial Pterygoid(Main trunk of C.N. V3)
  1. Elevates Mandible
  2. Protude mandible
  3. Grinding movement
Don’t Forget to Solve all the previous Year Question asked on MUSCLES OF MASTICATION

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