Muscles of Mastication

1. MUSCLES OF MASTICATION
By: Dr Prasanna Kumar P

2. CONTENTS
 INTRODUCTION
 EMBRYOLOGY
 PRIMARY MUSCLES OF MASTICATION
 ACCESSORY MUSCLES OF MASTICATION
 MOVEMENTS OF THE MANDIBLE
 ASSESSMENT OF MUSCLES OF
MASTICATION
 REFERENCE

3. INTRODUCTION:
 Mastication is the process of chewing food in
preparation for deglutition and digestion.
 All primary muscles of mastication originate on
the skull and insert on the mandible.
 They move the mandible during mastication and
speech.
 Movements of the mandible are classified as:
● Elevation
● Depression
● Protrusion
● Retrusion
● Side-to-side (lateral) excursion

4. INTRODUCTION:
 They are:
The masseter
The temporalis
The lateral pterygoid
The medial pterygoid

5.  The accessory muscles of mastication
are the:
 Digastric
 Mylohyoid
 Geniohyoid
 Buccinator

6. EMBRYOLOGY
 The muscles of mastication arise
from the mesoderm
of first pharyngeal arch.
 They are then differentiated into
muscles starting the seventh week.
 The nerve supply to these muscles
begins by the eighth week, supplied
by the mandibular nerve which is the
nerve of that arch.

7. MASSETER MUSCLE
 The masseter muscle is a
powerful muscle of
mastication that elevates the
mandible.
 It overlies the lateral surface
of the ramus of mandible.
 The masseter muscle is
quadrangular in shape.
 It is anchored above to the
zygomatic arch and below to
most of the lateral surface of
the ramus of mandible.

8. MASSETER MUSCLE
 The more superficial part of
the masseter:
 Origin: Inferior border of the
anterior 2/3rd of zygomatic
arch.
 Insertion: Into the angle of
mandible and inferior and
lateral parts of the ramus of
the mandible.

9. MASSETER MUSCLE
 The deep part of the
masseter:
 Origin: Medial border of the
zygomatic arch and inferior
border of the posterior 1/3rd
of the zygomatic arch.
 Insertion: Into the central and
upper part of the ramus of
mandible as high as the
coronoid process.

10. MASSETER MUSCLE
 Nerve supply: Masseteric
nerve from the
mandibular nerve [V3].
 Blood Supply: The
masseteric artery from
the maxillary artery.
 The masseteric nerve and
artery originate in the
infratemporal fossa and
pass laterally over the
margin of the mandibular
notch to enter the deep
surface of the masseter
muscle.

11. MASSETER MUSCLE
Function:
 As fibers of the masseter
contract, the mandible is elevated
and the teeth are brought into
contact.

12. MASSETER MUSCLE
 Superficial fibres cause
protrusion.

13. SUBMASSETERIC SPACE
 Situated between the masseter
muscle and the lateral surface
of the ascending ramus of the
mandible.
 The submasseteric space is
involved by infection as a
result of:
 Spread from the buccal space
 From soft tissue infection
around the mandibular third
molar (pericoronitis).
 An infected mandibular angle
fracture

14. SUBMASSETERIC SPACE
 When the submasseteric space
is involved, the masseter
muscle also becomes inflamed
and swollen.
 Because of the involvement of
the masseter muscle, the patient
also has moderate to severe
trismus caused by
inflammation of the masseter
muscle.
 The treatment of a
submasseteric space infection
is usually by surgical incision
and drainage.

15. MANAGEMENT
 It involves 5 goals:
 Medical support of the patient, with
special attention to protection of the
airway.
 Surgical removal of the source of
infection as early as possible.
 Surgical drainage of the infection, with
proper placement of drains.
 Administration of antibiotics in
appropriate doses.
 Frequent re-evaluation of the patient.

16.  The temporalis muscle is a large,
fan-shaped muscle that fills much
of the temporal fossa.
 Origin: From the bony surfaces of
the fossa superiorly to the inferior
temporal line and is attached
laterally to the surface of the
temporal fascia.
 Insertion: It attaches down the
anterior surface of the coronoid
process and along the related
margin of the ramus of mandible,
almost to the last molar tooth.
TEMPORALIS MUSCLE

17. TEMPORALIS MUSCLE
 The more anterior fibers are
oriented vertically while the more
posterior fibers are oriented
horizontally.
 The fibers converge inferiorly to
form a tendon, which passes
between the zygomatic arch and
the infratemporal crest of the
greater wing of the sphenoid to
insert on the coronoid process of
the mandible.

18. TEMPORALIS MUSCLE
Nerve supply: Anterior and
posterior deep temporal branches
from the mandibular division of
trigeminal nerve.
Blood supply: Anterior, posterior,
and superficial temporal arteries.

19. TEMPORALIS MUSCLE
 Deep temporal arteries
 Two in number
 These vessels originate from the
maxillary artery in the
infratemporal fossa and travel
with the deep temporal nerves
around the infratemporal crest of
the greater wing of the sphenoid
to supply the temporalis muscle.
They anastomose with branches
of the middle temporal artery.

20. TEMPORALIS MUSCLE
 Middle temporal artery
 The middle temporal artery
originates from the superficial
temporal artery.
 It penetrates the temporalis fascia,
passes under the margin of the
temporalis muscle, and travels
superiorly on the deep surface of
the temporalis muscle.
 The middle temporal artery
supplies the temporalis and
anastomoses with branches of the
deep temporal arteries.

21. TEMPORALIS MUSCLE
Function:
 When the temporal muscle
contracts, it elevates the
mandible and the teeth are
brought into contact.

22. TEMPORALIS MUSCLE
Function:
 The temporalis also retracts the
mandible or pulls it posteriorly.

23. TEMPORALIS MUSCLE
Function:
 The temporalis participates in
side-to-side movements of the
mandible.

24. TEMPORALIS MUSCLE FLAP
 Useful for reconstruction of
defects in the region of the
auricle, the orbit, infratemporal
fossa, and the hard palate and
intraoral defects.
 After freeing its origin, the
muscle can be turned
posteriorly over a defect in the
auricular area or moved
anteriorly to fill the orbit.
 Most commonly it is directed
towards the orbit, the
infratemporal fossa, or the hard
palate.

25. TEMPORALIS MUSCLE FLAP FOR RECONSTRUCTION OF
DEFECT IN HARD PALATE
The flap is tunneled deep to zygomatic arch and sutured to the buccal and palatal mucosal
margins with resorbable sutures to fill the defect.

26. DEFECT IN THE AURICULAR AREA COVERED WITH A
TEMPORALIS FLAPAND LATE FOLLOW-UP.

27. GILLIES APPROACH
 First described by Gillies, Kilner,
and Stone in 1927.
 Used to reduce zygomatic arch
fractures.
 The temporal fascia is attached to the
zygomatic arch and the temporal
muscle passes downward medial to
the fascia to be attached to the
coronoid process.

28. GILLIES APPROACH
 An incision of approx. 2-2.5cm
is made in the hair-bearing area
of the scalp, approximately
2cm above and 1cm anterior to
the ear.
 The dissection continues down
to the glistening white deep
temporal fascia.
 The temporal fascia is incised
horizontally to expose the
temporalis muscle.

29. GILLIES APPROACH
 A sturdy elevator, like Rowe
zygomatic elevator, is inserted
deep to the fascia.
 The elevator must pass between
the deep temporal fascia and
temporalis muscle.
 The bone should be elevated in an
outward and forward direction,
with care taken not to put force on
the temporal bone.

30. GILLIES APPROACH
 The snap sound will be
heard as soon as reduction
procedure is complete.
 The elevator is withdrawn
and wound is closed in
layers.

31. PTERYGOIDEUS MEDIALIS
 The medial pterygoid muscle is
quadrangular in shape.
 It has deep and superficial heads.
 Superficial head:
- Origin: Maxillary tuberosity and
pyramidal process of the palatine
bone.
- Insertion: Medial surface of
ramus and angle of the mandible.
 Deep head:
- Origin: Medial surface of lateral
pterygoid plate.
- Insertion: Medial surface of ramus
and angle of the mandible.

32. MEDIAL PTERYGOID
 Nerve supply: Nerve to
medial pterygoid, branch of
the main trunk of
mandibular nerve.
 Blood supply: Pterygoid
branch of the maxillary
artery

33. MEDIAL PTERYGOID
 Along with the masseter, it
forms a muscular sling that
supports the mandible at the
mandibular angle.

34. MEDIAL PTERYGOID
 When its fibers contract, the
mandible is elevated and the
teeth are brought into contact.

35. MEDIAL PTERYGOID
 Since it passes obliquely
backward to insert into the
mandible, it also assists the
lateral pterygoid muscle in
protruding the lower jaw.

36. MEDIAL PTERYGOID
 Right medial pterygoid
with right lateral pterygoid
turn the chin to left side.

37. PTERYGOIDEUS LATERALIS
 The lateral pterygoid is a thick
triangular muscle.
 It has two heads: The upper head
and lower head.
 Upper head(small):
- Origin: From greater wing of
sphenoid and infratemporal crest.
- Insertion: Articular disc and
capsule of the TMJ.
 Lower head (larger):
- Origin: lateral surface of
pterygoid plate of sphenoid bone.
- Insertion: pterygoid fovea on the
neck of the condyle of the mandible.

38. LATERAL PTERYGOID
 Nerve supply: Lateral pterygoid
branches (for each head) from
the mandibular division of the
trigeminal nerve.
 Blood supply: Pterygoid branch
of the maxillary artery

39. LATERAL PTERYGOID
 FUNCTIONS:
 Depresses mandible to open mouth,
with suprahyoid muscles.

40. LATERAL PTERYGOID
 FUNCTIONS:
 Lateral and medial pterygoids
protrude mandible.

41. LATERAL PTERYGOID
 FUNCTIONS:
 Right lateral pterygoid and right
medial pterygoid turn the chin to
left side.

42. Accessory Muscles of
Mastication
 Suprahyoid muscles
-The suprahyoid muscle group is
made up of:
- digastric muscle
- mylohyoid muscle
- geniohyoid muscle

43. SUPRAHYOID MUSCLES
 The suprahyoid muscles connect
the hyoid bone with the skull.
 Their basic functions are
elevation of the hyoid bone and
depression of the mandible.

44. Digastric Muscle
 It consists of two bellies united by
an intermediate tendon.
 The posterior belly arises from the
mastoid notch of the temporal
bone.
 The anterior belly is shorter and
attaches to the lower border of the
mandible at the digastric fossa
close to the symphysis.
 Nerve supply:
 Posterior belly- Digastric branch of
the facial nerve
 Anterior belly- Mylohyoid branch
of the inferior alveolar nerve.

45. Digastric Muscle
 Function: Depresses the
mandible and elevates the
hyoid bone.

46. Mylohyoid Muscle
 Arise from the mylohyoid line
on the internal surface of the
mandible from the third molar
region posteriorly to almost the
symphysis anteriorly.
 The direction of the fibers is
toward the midline, where they
form a tendinous raphe.
 Nerve supply:
 Mylohyoid branch of the
inferior alveolar nerve.
 Blood supply: Submental
artery, which is a branch of the
facial artery.

47. Mylohyoid Muscle
 Function: Elevation of the
tongue.

48. Geniohyoid Muscle
 It is situated above the
mylohyoid muscle and arises
from the inferior genial
tubercle behind the
mandibular symphysis.
 It inserts into the front of the
body of the hyoid bone.
 Nerve supply: Hypoglossal
nerve.
 Action: To pull the hyoid bone
up and forward, or to pull the
mandible down and
posteriorly.

49. Buccinator
 Origin:
 Upper fibres- from maxilla
opposite molar teeth.
 Lower fibres- From mandible
opposite molar teeth.
 Middle fibres- from
pterygomandibular raphe.
 Insertion:
 Upper fibres- straight to
upper lip
 Lower fibres- straight to
lower lip
 Middle fibres deccusate

50. Buccinator
 Function: Flattens cheek
against gums and teeth;
prevents accumulation of
food in the vestibule.
 It is the whistling muscle.

51. Movements of the mandible
 Depression
 It is generated by the digastric,
geniohyoid, and mylohyoid muscles
on both sides, is normally assisted by
gravity and, because it involves
forward movement of the head of
mandible onto the articular tubercle,
the lateral pterygoid muscles are also
involved.

52. Movements of the mandible
 Elevation:
 It is a very powerful movement
generated by the temporalis,
masseter, and medial pterygoid
muscles.

53. Movements of the mandible
 Protrusion:
 It is mainly achieved by the lateral
pterygoid muscle, with some
assistance by the medial pterygoid.

54. Movements of the mandible
 Retraction:
 It is carried out by the geniohyoid
and digastric muscles, and by the
posterior fibers of the
temporalis and deep part of
masseter muscles, respectively.

55. Movements of the mandible
 Lateral movements:
 Eg. Chewing
 Chewing from right side involves left
lateral pterygoid, left medial pterygoid
(push the chin to right side)
 Then right temporalis (ant. fibres) and
right masseter (deep fibres) chew the
food.

56. MOVEMENTS OF THE MANDIBLE

57. ASSESSMENT OF MUSCLES
OF MASTICATION
 MASSETER:
- It is palpated bilaterally at its
superior and inferior
attachments.
- First, the fingers are placed on
each zygomatic arch (just
anterior to the TMJ).
- They are then dropped down
slightly to the portion of the
masseter attached to the
zygomatic arch, just anterior
to the joint to palpate the deep
masseter.

58. ASSESSMENT OF MUSCLES
OF MASTICATION
 MASSETER:
 Then fingers drop to the
inferior attachment on the
inferior border of the ramus.
The area of palpation is
directly above the attachment
of the body of the superficial
masseter.
 The patient is asked to report
any discomfort or pain.

59. ASSESSMENT OF MUSCLES
OF MASTICATION
 Functional manipulation of the
medial pterygoid muscle
 It is an elevator muscle and therefore
contracts as the teeth are coming
together. If it is the source of pain,
clenching the teeth together will
increase the pain.
 The medial pterygoid stretches when
the mouth is opened wide. Therefore
if it is the source of pain, opening the
mouth wide will increase the pain.

60. ASSESSMENT OF MUSCLES
OF MASTICATION
 Functional manipulation of the
inferior lateral pterygoid muscle
 The patient is asked to protrude
mandible against resistance provided
by the examiner. If it is the source of
pain, this activity will increase the
pain.
 The inferior lateral pterygoid
stretches when the teeth are in
maximum intercuspation. Therefore
if it is the source of pain when the
teeth are clenched, the pain will
increase.

61. ASSESSMENT OF MUSCLES
OF MASTICATION
 Functional manipulation of the
superior lateral pterygoid muscle
 The superior lateral pterygoid
contracts with the elevator muscles,
especially clenching. Therefore if it is
the source of pain, clenching will
increase the pain.
 If a tongue blade is placed between
the posterior teeth bilaterally and the
patient clenches on the separator,
pain again increases with contraction
of the superior lateral pterygoid.

62.  TEMPORALIS:
 The temporalis is divided into
three functional areas, each of
which is independently palpated.
 The anterior region is palpated
above the zygomatic arch and
anterior to the TMJ. Fibers of this
region run essentially in a vertical
direction.
ASSESSMENT OF MUSCLES
OF MASTICATION

63.  TEMPORALIS:
 The middle region is palpated
directly above the TMJ and
superior to the zygomatic arch
where fibers run in an oblique
direction across the lateral
aspect of the skull.
 The posterior region is
palpated above and behind the
ear where fibers run in
horizontal direction.
ASSESSMENT OF MUSCLES
OF MASTICATION

64.  TEMPORALIS:
 The posterior region is
palpated above and behind the
ear where fibers run in
horizontal direction.
ASSESSMENT OF
MUSCLES OF
MASTICATION

65.  TEMPORALIS:
 The tendon of the temporalis is
palpated by placing the finger of
one hand intraorally on the anterior
border of the ramus and the finger
of the other hand extraorally on the
same area.
 The intraoral finger is moved up
the anterior border of the ramus
until the coronoid process and
tendon are palpated.
 The patient is asked to report any
discomfort or pain.

66. REFERENCE
 Gray’s Anatomy for Students 2nd edition.
 GRAYS ANATOMY ATLAS 2ND EDITION
 Netter - Head and Neck Anatomy for Dentistry 2ND edition
 Vishram Singh Textbook of Anatomy Head, Neck, and Brain 2nd edition
 B D Chaurasia’s Human Anatomy vol. III - 2nd edition

67. Thank you!