PRESENTATION INCLUDES 4 DIFFERENT MUSCLES OF MASTICATION

1. DR MEENAL ATHARKAR
ENDODONTIST

2.  Introduction
 Basic considerations
 Embryological aspects
 Nervous control
 Primary muscles of mastication
 Accessory muscles of mastication
 Blood supply
 Nerve supply
 Applied aspect

3.  Muscles have variety of roles in our body
including protecting our bones and keeping
our body moving which also includes the
movement which is required for the process
of mastication that is nothing but chewing of
food.

4.  Def of muscle - Tissue characterized by the
aggregation of cells whose primary role is to
produce contraction, causing and allowing
movements of parts and organs of the body.
 A band of contractile fibrous tissues, which
produces movements in a body.

5.  Mastication - Rhythmic opposition and
separation of jaws with the involvement of
teeth , lips, cheeks, tongue for chewing of
food in order to prepare it for swallowing
and digestion.
 Also known as chewing

7.  Musculus = mouse, hence MUSCLE.
 What is a muscle?
 Part of muscle?
Is a contractile tissue which brings about movements.
Muscle
Two ends
Origin Insertion
Two parts
Fleshy
Connective
tissue core

8.  According to characteristics:
Skeletal
• Most common
• Best
differentiated
• Highest
nervous
control
Smooth
• Surrounds
viscera
• Regulation of
internal
environment
• Less
dependant on
nervous
control
Cardiac
• Myocardium
• Intermediate
• Automatic
and rhythmic
contractions

9.  Histopathological features:

12.  According to type of fibers:
Type 1
• Slow
• Tonic
contraction
• Red color-
myoglobin
• Resistant to
fatigue
Type 2
• Fast
• Phasic
contraction
• Paler color
• Easy
fatiguability
Intermediate
• Mixture of
both

13.  According to fascicular architecture:
• Quadrilateral
• Straplike
• Fusiform
Parallel
• Unipennate
• BipennateOblique
• Cruciate
• TwistedSpiral

14.  Sarcolemma- covering of each muscle fiber.
 Endomysium- loose connective tissue outside
external lamina.
 Perimysium- heavier connective tissue
surrounding bundle of muscle fiber.
 Epimysium- heavier connective tissue with
dense collagen grouping many fascicules.

16.  Each muscle fiber is filled with many
myofibrils.
 In between myofibrils, sarcoplasm is present
consisting of organells(e.g. mitochondria,
glycogen granules,etc).
 Protein components- actin and myosin.
 Highly organized structural units- sarcomere.

17.  Dark- A band(Anisotropic)
 Light- I band(Isotropic)
 Sarcomere= ½ I band+ 1 A band+ ½ I band(area
between two z line).
 Z disc- for attachment of actin.
 H zone= only myosin present.
 M line= dark band attached to center of myosin
filament.

19. Splancnic
mesoderm
Cardiac
muscle
Smooth
muscle
Paraxial
mesoderm
Skeletal
muscle

20.  Mesodermal derivatives of 1st branchial arch.

21.  Four major types of sensory receptors:
1) Muscle spindles
2) Golgi tendon organs
3) Pacinian corpuscles
4) Nociceptors

22. 1. Myotactic/ stretch reflex:
Important for resting position of jaw.
2. Nociceptive reflex/ flexor reflex:
Protects teeth and supporting structures
Also called as Antagonist Inhibition.

25.  Small forces – periodontal receptors
 Large forces – mechano receptors in bony
socket.
 Important in fine tuning and modulating jaw
movements.

26.  Primary muscles of mastication:-
Masseter Temporalis
Medial
pterygoid
Lateral
pterygoid

27. Muscle Origin Insertion Nerve Actions
Masseter
Superficial
Middle
Deep
Ant 2/3 lower border
Zy arch
Ant 2/3 deep surface &
post 1/3 lower border
Zy arch
Deep surface—Zy arch
Lower part of lat
surface Ramus
Middle part Ramus
Upper part- Ramus &
coronoid process
Masseteric
Branch Of
Mandibular
(ant div)
Elevates
mandible

28. Muscle Origin Insertion Nerve Actions
Temporalis
(Fan shaped)
Temporal fossa
& fascia
Coronoid process
Anterior border of
ramus
2 deep temporal
branches of
Mandibular Nerve
Elevates
Retracts
Side to side

29. Muscle Origin Insertion Nerve Actions
Medial pt
Quadrilateral
Superficial
Deep
Tuberosity –
maxilla
Medial
surface-
lateral
pterygoid
Medial surface of angle
& Ramus
Mylohyoid groove
Nerve to medial
pterygoid. branch. of
main trunk of
Mandibular Nerve.
Elevates
mandible
Protrude
Turn chin to
side.

30. Muscle Origin Insertion Nerve Actions
Lateral
Pterygoid
Upper
Lower
Infratemporal surface
Crest – greater wing
of sphenoid
Lat suface-lat
pterygoid plate
Pterygoid fovea
Articular disc
&Capsule of TMJ
Branch-
Anterior div
of
Mandibular
Nerve
Depress mand
Turns chin to side
With medial
pterygoid
protrudes mand.

31. 1. Digastric muscle
2. Mylohyoid muscle
3. Geniohyoid muscle
4. Buccinator muscle
5. Infrahyoid muscles

32. Muscle Origin Insertion Nerve Actions
Digastric Anterior
belly-
digastric
fossa
Posterior
belly-
mastoid
notch
Into tendon attached to
body and greater cornu
of hyoid bone
Anterior belly-
mylohyoid branch of
inf alv nerve.
Posterior belly- facial
nerve
Depresses
mandible while
openin mouth &
elevates hyoid
bone during
swallowing.

33. Muscle Origin Insertion Nerve Actions
Mylohyoid Mylohyoid
line of
mandible
Post fibres- body of
hyoid bone
Middle & ant fibers
dicussate to form
fibrous band
Mylohyoid branch of
inf alv nerve.
Depresses
mandible while
openin mouth &
elevates hyoid
bone and floor
of mouth during
deglutition.

34. Muscle Origin Insertion Nerve Actions
Geniohyoid Inferior
genial
tubercle of
mandible
Anterior surface of
hyoid bone
1st cervical spinal
nerve through
hypoglossal nerve
Depresses
mandible while
openin mouth &
elevates hyoid
bone and during
deglutition.

35. Muscle Origin Insertion Nerve Actions
Buccinator Upper part
maxilla opp
molars
Lower part
mand opp
molars
Middle part
pterygomandi
bular raphe
Into upper lips
Into lower lips
Decussate before
passing to the lips
Facial nerve Flattens
cheeks.
Fine tunes the
mandibular
movements

36. Sternohyoid
• Depresses hyoid
bone
Sternothyroid
• Depresses larynx
Thyrohyoid
• Depresses hyoid
• Elevates larynx
Omohyoid
• Depresses hyoid
bone

37.  Arterial supply:
 Maxillary artery – second part.
 Terminal branch of ECA
 Divided into 3 parts
 Second part supplies muscles of mastication

38.  Venous drainage:
 Retromandibular vein

39.  Lymphatic drainge:
 Submandibular lymph nodes
 Sublingual lymph nodes

40.  All muscles of mastication are supplied by
mandibular nerve.

42.  Travell – reported 1st
 Schwartz – explained psychologic
involvement
 Localized tender area.
 Any muscle can be involved-common are
head, neck, shoulder and lower back.

43.  Most common cause of facial pain after tooth
ache.
 Age  20-40yrs
 M:F = 1:4
 Consequence of overuse of muscles or
chronic microtrauma.

44.  Laskin’s four cardinal signs:
Unilateral pain
Muscle tenderness
Clicking and popping
noise in TMJ
Limitation of jaw
movements

45.  Laskin’s two negative signs:
Absence of any
organic
changes in TMJ
No tenderness
on palpation

46.  Treatment-
 Relieve of emotional factor
 Correction of faulty restoration or prosthesis
 Muscle exercises and physiotherapy
 Drugs like muscle relaxant and analgesics.

47.  Prominent symptom – difficulty in chewing
 Easy fatigability of muscles
 Autoimmune disorder
 Idiopathic in nature
 Antibodies against AChR at NMJ of skeletal
muscle
 Common in middle age.

48.  W>M
 Tires out before chewing of bolus
 Mouth may often remain open.
 Weakness in muscles of tongue and soft
palate – entry of water in nasal cavity.
 Treatment physostigmine – drug of choice
though temp.

49.  Massetric hypertrophy  very common
 Causes –
 Congenital facial hypertrophy
 Functional hypertrophy

50.  Any non synchronized contractions of lateral
pterygoids
 Causes deviation of jaw.
 Commonly seen in bruxism, stress, etc.
 Common cause for MPDS.

51.  In the jaw example above, absence of right
LP contraction results in a left excursive
movement.
 Deviations upon opening are most likely
due to differences in tension of the two
lateral pterygoids.

52.  To survive, we must meet the nutritional
requirements of the physiologic system by
obtaining food & assimilating it within the
body
 Adds pleasure to eating by increasing the
appreciation of the taste of food.

53.  “Preventing the preventable”
 Myofacial pain – most common cause of non
dental pain in oro facial region.
 Hence its major responsibility for diagnosis
and treatment of such conditions as we being
stomatologists.

54.  Emphasis should always be on conservative
therapy that facilitates the musculoskeletal
system 's natural capacity to heal.
 Cases which require greater expertise have
to be referred to other clinicians of
appropriate field.