muscles of mastication

1. THE
MUSCLES OF MASTICATION
DR.ATHUL CHANDRA.M
First year PostGraduate

2. CONTENTS
1) INTRODUCTION
2) DEVELOPMENT
3) MUSCLES OF MASTICATION
4) PHYSIOLOGY
5) CONCLUSION

3. MASTICATION
 Rhythmic opposition & separation of jaws with the involvement of teeth, lips, cheeks,
tongue for chewing of food in order to prepare it for swallowing and digestion.
 Main purpose of mastication is to reduce the size of food particles to a size that is
convenient for swallowing (Bolus formation) with the help of saliva.
“ “

4. THE DEVELOPMENT OF MUSCLES
• The muscular system develops from intraembryonic mesoderm.
• Muscle tissues develop from embryonic cells called myoblast.
• Muscular component of Branchial arch form many striated muscles in the
head and neckregion.
• Muscles of mastication are derived from the first arch called the
MANDIBULAR ARCH.

6. MUSCLES OF MASTICATION
• These are the muscles that move the mandibleduring
mastication, speech &deglutition.
• They move the mandible quickly & precisely to enable
different speech sounds that are to be made in rapid
succession and they are also capable ofexerting enormous
forces that are required to break down tough foods.

7. PRIMARY MUSCLES OF MASTICATION
• MASSETER
• TEMPORALIS
• LATERAL PTERYGOID
• MEDIAL PTERYGOID • TEMPORALIS

8. SECONDARY MUSCLES OF MASTICATION
The suprahyoid group of muscles being used as secondary or
supplementary muscles.
They are:
 Digastric
 Mylohyoid
 Geniohyoid

9. MASSETER
• a quadrilateral muscle
• covers most of the lateral aspect of the
ramus
• It consists of threelayers which blend
anteriorly

10.  Superficial layer (largest):
 Origin:
From anterior 2/3 of lower border of
zygomatic arch and adjoining zygomatic
process of maxilla. Fibers pass downward
and backwards at an angle of 45 degree.
 Insertion:
Into lower part of lateral surface of
ramus of mandible

11.  Middle layer:
 Origin:
From anterior 2/3 of deep surface and
posterior 1/3 of lower border of
zygomatic arch.
Middle and deep fibres pass vertically
downwards.
 Insertion:
Into middle part of ramus.
 Deep layer:
 Origin:
From deep surface of zygomatic arch.
 Insertion:
Into upper part of ramus and coronoid process of
mandible.
Three layers are separated posteroinferiorly
by an artery and a nerve

12.  Nerve supply:
Masseteric nerve, a branch of anterior division of
mandibular nerve
 Blood supply:
Maxillary artery, which is a branch of external carotid
artery.

13. • a powerful elevator of the mandible & isvery active
during forceful clenched (centric)occlusion.
• Deep head exerts primarily a vertical force on the
mandible.
• Superficial head exerts vertical & directed force.
• It also helps in ipsilateral excursion

14. TEMPORALIS
fan shaped muscle that fills the temporal fossa
 Origin:
 Temporal fossa excluding zygomatic bone.
 Temporal fascia
 Fibres Converge and pass through gap deep to
zygomatic arch.
 Insertion:
 Margins and deep surface of coronoid process.
 Anterior border of ramus of mandible.

15.  Nerve supply:
Two deep temporal branches from anterior division of
mandibular nerve.
 Blood supply:
Deep temporal part of maxillary artery.
ACTIONS
• Elevates the mandible,this movement requires both the upward pull of
anterior fibers and backward pull of the posteriorfibers.
• Posterior fibers draw the mandible backwards after it has been protuded.
• It is also a contrbutor to side to sidegrinding movement.
• Posterior fibers pull the protruded mandible back to centric occlusion.
• It helps in ipsilateral excursion.

16. LATERAL PTERYGOID
 SHORT, CONICAL, HASUPPER AND LOWER HEADS.
 ORIGIN:
 UPPER HEAD(small):
 From infratemporal surface and crest of greater wing of sphenoid bone.
 LOWER HEAD(larger):
 From lateral surface of lateral pterygoid plate.
 Fibers run backwards and laterally and converge
 INSERTION:
 PTERYGOID FOVEA
 On the anterior surface of neck of mandible
 Anterior margin of articular disc and capsule of temperomandibular joint.Insertion
is posterolateral and at a slightly higher level than origin.

17.  Nerve supply:
 A branch of anterior division of
mandibular nerve
 Blood supply:
 Pterygoid branch of 2nd part of maxillary
artery.
 ACTIONS OF LATERAL PTERYGOIDMUSCLE:
 Depress mandible to open mouth, with suprahyoid muscle
 Protract mandible
 Left lateral pterygoid and right medial pterygoid turn the chin to left
side as part of grinding movements.

18. MEDIAL PTERYGOID
Quadrilateral, has a smallsuperficial and a large deep head.
 ORIGIN:
SUPERFICIAL HEAD (SMALLSLIP):
 From tuberosity of maxilla and adjoining bone.
DEEP HEAD (QUITE LARGE):
 From medial surface of lateral pterygoid plate and adjoining process of palatine
bone.
 Fibres run downwards,backwards and laterally.
 INSERTION:
 Roughened area on the medial surface of angle and adjoining ramus of
mandible, below and behind the mandibular foramen and mylohyoid groove.

19.  NERVE SUPPLY:
 Nerve to medial pterygoid, branch of main trunk of
mandibular nerve.
 BLOOD SUPPLY:
 Pterygoid branch of 2nd part of maxillaryartery.
ACTIONS
• Assits in elevating the mandible
• Acting with the lateral pterygoid they protrude it
• Right medial pterygoid with left lateral pterygoid turns the chin
to left side.

20.  DIAGASTRIC MUSCLE: Two bellies united by
tendon
 Origin –
 Anterior belly from diagastric fossa of mandible.
Posterior belly from mastoid notch of temporal
bone.
 Insertion –Both meet at the intermediate tendon
and held by the fibrous pulley.
 ACTIONS:
 Muscle - secondary role in mastication as depressor muscle
+ to action of lateral pterygoid when mouth to be opened
against resistance.
 Elevation of hyoid bone

21.  MYLOHYOID MUSLE: Flat
triangular
 Origin –Mylohyoid line of mandible.
 Insertion – Middle & Anterior fibers into median
raphae. Posterior fibers body of hyoid bone.
 ACTION:
 The secondary role of this muscle is evident as a depressor seen
in action when
mouth is to be opened against resistance.
 It elevates the floor of mouth to help in deglutition

22.  GENIOHYOID: Short and narrow
muscle lies above mylohyoid
 Origin –Inferior mental spine
 Insertion – Anterior surfaceof body of
hyoid bone
 ACTIONS:
 Geniohyoid elevates the hyoid bone and draws it forward, thus acting as a
partial antagonist to stylohyoid.
 When the hyoid bone is fixed, it depresses the mandible

23. PALPATION OF MASTICATORY
MUSCLES
 Digital palpation: Regional muscles are examined for the tenderness and trigger points using the digital
palpation.
 Temporalis muscle: Temporalis muscle can be seen and readily palpated throughout entire length and
breadth when the patient’s teeth are firmly clenched.
 Masseter muscles: They are most effectively examined by simultaneously pressing them from inside and
outside the mouth in the process of bimanual palpation.
Masseter muscle
Temporalis muscle

24.  Lateral pterygoid muscle: The lateral pterygoid muscles are
evaluated by inserting a finger each behind the maxillary
tuberosities.
 Medial pterygoid is checked by running a finger in an
anteroposterior direction along the medial aspect of the
mandible in the floor of mouth
Lateral pterygoid
Medial pterygoid

25. CONCLUSION
• The masticatory system is extremely complex,primarily
made of bones,muscles,ligaments and teeth.
• Precise movement of mandible by the musculature is
required to move the teeth effectively across each other
during function.
• The knowledge of the anatomy physiology and mechanisms
of these muscles are basic tounderstand the movements.