Mastication is a harmonious and skillful activity which requires the presence and co ordination of not only the muscles of mastication but also the supra infra-hyoid muscles, and the facial muscles BASIC MUSCLES: Temporalis Masseter Medial Pterygoid Lateral Pterygoid

1. MUSCLES OF
MASTICATION

2. Mastication is a harmonious and skillful activity
which requires the presence and co ordination of not
only the muscles of mastication but also the supra
infra-hyoid muscles, and the facial muscles

3. • BASIC MUSCLES:
Temporalis
Masseter
Medial Pterygoid
Lateral Pterygoid

5. • ACCESSORY MUSCLES
Muscles of tongue, lip
& cheek
Suprahyoid muscles
Mylohyoid
Geniohyoid
Stylohyoid
Digastric muscle
(anterior belly)
Infrahyoid muscles:
Sternothyroid
Thyrohyoid
Omohyoid
Sternohyoid

6. DEVELOPMENT
• The basic muscles of mastication develop
from the mesoderm of the first pharyngeal
arch.

7. • So they receive all their innervations
from the mandibular branch of the
trigeminal nerve, all from the anterior
division except the medial pterygoid
which gets its nerve supply from the
main trunk.

8. MOVEMENTS OF
MANDIBLE
• Movements that the mandible can undergo are:
1. Depression: As in opening the mouth.
2. Elevation: As in closing the mouth.
3. Protraction: Horizontal movement of the mandible
anteriorly.
4. Retraction: Horizontal movement of the mandible
posteriorly.
5. Rotation: The anterior tip of the mandible is “slewed”
from side to side.

9. • These movements of mandible are performed by various
muscles involved in it. So, functionally, the muscles of
mastication are classified as:
• Jaw elevators:
•Masseter
•Temporalis
•Medial pterygoid
• Jaw depressors:
•Lateral pterygoid
•Anterior digastric
•Geniohyoid
•Mylohyoid

10. TEMPORALIS
It is the largest among all the mastication
muscles and is a fan shape muscle.
It has been divided into 2 heads:
 Deep head (anterior, middle and posterior
fibers)
 Superficial head (much smaller)

11. Origin:
From the inferior
temporal line , floor of
the temporal fossa and
from the overlying
temporal fascia of the
side of the skull.
Insertion:
Superior border and
medial tip of the
coronoid process.

12. • Action:
• Elevation (anterior
fibers)
• Retraction
(posterior fibers)
• Nerve supply:
• Anterior division of
the mandibular
nerve
(by two deep
temporal nerves)

13. •Blood Supply
•This is furnished by the middle & deep
temporal arteries. The middle temporal artery
is a branch of the superficial temporal artery &
the deep temporal arteries are branches of the
maxillary artery

14. PALPATION
The muscle is divided into three functional areas and
therefore each area is independently palpated.
The anterior region is palpated above the zygomatic
arch and anterior to the TMJ .

15. The middle region is palpated directly above the
TMJ and superior to the zygomatic arch .

16. • The posterior region is palpated above and
behind the ear.
• If uncertainty arises regarding the proper
finger placement. The patient is asked to
clench the teeth together so that the temporal
muscle contracts and the fibers should be felt
beneath the finger tips.

17. MASSETER
It consist of three overlapping layers:
The origin of the whole muscle is mainly
from the zygomatic process which consists
of :
The superficial layer
The middle layer
The deep layer

18. SUPERFICIAL LAYER
It is the largest component that arises from the anterior two
thirds of the lower border of the zygomatic arch.
Its fibers run downwards and backwards and inserts into
lower half of the ramus including angle of the mandible.

19. The middle layer takes its origin from the medial surface of the
anterior two-thirds and the lower border of posterior one third
of the arch.
The fibers run more directly downwards to be inserted into
lateral surface of the middle part of the ramus.
MIDDLE LAYER

20. The deep layer arises from the whole length of medial surface
of the zygomatic arch.
The fibers pass downwards to attach to the upper part of the
mandible ramus.
DEEP LAYER

21. • Action of masseter is mainly to elevate the
mandible (antigravity action) and also helps
in protrusive movement.
• It is the main powerful muscle involved in
the elevation of the mandible

22. •Nerve supply
•Supplied by Masseteric nerve a branch of anterior
division of Mandibular nerve
•Blood Supply
•Supplied by masseteric artery branch of maxillary
artery

23. PALPATION
• The patient is asked to clench their teeth
and, using both hands, the practitioner
palpates the masseter muscles on both
sides extraorally, making sure that the
patient continues to clench during the
procedure.
• Palpate the origin of the masseter
bilaterally along the zygomatic arch and
continue to palpate down the body of the
mandible where the masseter is attached.

24. D-Palpation of the
masseter muscles
E-Bimanual palpation of
the masseter muscles

25. MEDIAL PTERYGOID
• It is also called as the Pterygoideus internus (Internal
pterygoid muscle).
• It consist of Two heads which differ in origin:
The superficial head
The deep head

26. •
• SUPERFICIAL HEAD
The superficial head originates from the
maxillary tuberosity & pyramidal process of
palatine bone

27. DEEP HEAD
The deep head originates from the medial surface of
lateral pterygoid plate of the sphenoid bone.

28. • Action:
1. Elevates the mandible .
2. Protrusion of the mandible (lateral & medial
pterygoid on one side protrude the
mandible to the opposite side).
3. Side to side movement (these lateral
movements are achieved by lateral & medial
pterygoid on both sides acting together to
produce side to side movements).

29. •Nerve Supply
•The never supplying the medial pterygoid
muscles is the medial pterygoid nerve branch of the
mandibular nerve
•Blood Supply
•The artery supplying the medial pterygoid
muscles is a branch of the maxillary artery

30. PALPATION
 It can be palpated by placing the finger on
the lateral aspect of the pharyngeal wall of
the throat, this palpation is difficult and
sometimes uncomfortable for the patient.
• Functional manipulation is done when the
muscle becomes fatigued and symptomatic.
The muscle contracts as the teeth are coming
in contact
Also stretches when the mouth is open wide.

31. G- Palpation of the medial pterygoid
muscle

32. LATERAL PTERYGOID
• Also called as the Pterygoideus externus
(External pterygoid muscle).
• It is a short conical muscle, having 2
heads:
upper and lower.

33. • Upper head:
• Origin: infra-temporal surface & crest of the
greater wing of sphenoid

34. • Lower head:
• Origin: Lateral surface of the lateral pterygoid
plate

35. • Actions of lateral pterygoid:
• Depression of the mandible .
• Side to side movement
(lateral movement) .
• Protrusion of the mandible.
• If the Pterygoid muscles of one side
act, the other side of the mandible is
drawn forward while the same
condyle remains comparatively fixed.

36. •Nerve Supply
•The nerve to the lateral pterygoid muscle
branches off from the masseteric or buccal nerve,
which is the branch of the anterior trunk of the
mandibular nerve
•Blood Supply
•Pterygoid vessels from Maxillary artery

37. PALPATION
The patient is asked to protrude the mandible against
resistance & Clench on maximum intercuspation
For Inferior lateral pterygoid :

38. • For Superior lateral pterygoid muscle:
The muscle contracts and stretches on
clenching.
In order to differentiate pain arising from
elevator muscle, the patient is asked to
open the jaw wide.

39. MASTICATORY MUSCLE
DISORDERS
Some of the common masticatory muscle
disorders involve:
• Congenital hyperplasia/ hypoplasia
• Hypermobility/ hypomobility of the
muscle
• Muscle pains
• MPDS
• Myositis ossificans etc.

40. CONGENITAL HYPOPLASIA/
HYPERPLASIA
• It occurs very rarely, and is more common
in masseter and orbicularis oris.
• Its oral symptoms include enlargement or
decreased size of the affected muscle,
which may show an asymmetric facial
pattern and stiffness in the temporo-
mandibular joint.
• It may or may not be associated with
hypermobility/ hypomobility of the
muscles.

41. MUSCLE HYPERMOBILITY/
HYPOMOBILITY
• This disorder involves extreme or diminished
activity of the masticatory muscles.
• Its etiology includes various factors such as:
• Decreased/ increased threshold potential of
neural activity.
• Parkinsonism
• Facial paralysis
• Nerve decompression
• Secondary involvement of systemic diseases.

42. MPDS
• Pain disorder in which unilateral
pain is referred from trigger
points in myofacial structure
• Constant pain, dull ache
Laskin’s Cardinal Signs
• Muscle tenderness
• Pain
• Clicking or propping noise in
TMJ
• Limited Jaw Movement

43. TEMPORAL TENDONITIS
• Chronic strain from temporalis muscle
pulling on tendon that attaches to
mandible
• Causes sharp headaches in temple just to
side of the eyes

44. CONCLUSION
• The masticatory muscles include a vital
part of the orofacial structure and are
important both functionally and
structurally.
• The proper management and periodical
self-examination of the muscles may
provide a greater chance of catching the
disease process at an early stage which
may be useful for its better prognosis.