Human Anatomy

1. MUSCLES OF MASTICATION
Masseter
Temporalis
Lateral Pterygoid
Medial Pterygoid

2. MASTICATORY SYSTEM
The masticatory system is a functional unit
composed
of the teeth; their supporting structures, the
jaws;
the temporomandibular joints; the muscles
involved directly
or indirectly in mastication (including the muscles
of the lips and tongue); and the vascular and
nervous
systems supplying these tissues. Functional and structural
disturbances in any one of the components of the
masticatory system may be reflected by functional or
structural disorders in one or more of its other components

3. MASTICATORY FUNCTIONS
Mastication is the action of
breaking down of food,
preparatory to deglutition.
This breaking-down action is
highly organized complex of
neuromuscular and
digestive activities that, in
normal individuals, integrate
the
various components of the
masticatory system, such as
the teeth and their investing
structures, the muscles, the
temporomandibular joints, the
lips, the cheeks, the palate,
the tongue, and the salivary
secretions.

4. MASTICATION- ORAL BEHAVIOUR
Mastication is oral motor behavior reflecting central
nervous system commands, and many peripheral
sensory
inputs to modulate the rhythmic jaw movements.
The action of masticatory muscles during chewing
varies between subjects in amplitude, onset timing, and
duration of the chewing cycle. However, it is possible to
recognize similarity between muscle actions. These wide
variations (within and between individuals) can be
explained
by differences related to individual occlusal contact
features and specific musculoskeletal morphology.
Since tooth guidance has an enormous influence on
muscle activity during chewing and swallowing, it is
advisable
to make restorations compatible with the functional
movement patterns of the patient rather than expect
the patterns of the mastication to adapt to the new
made restorations

5. CHEWING CYCLE
The masticatory sequence is the whole set
of movements
from ingestion to swallowing. It is made up
of masticatory
cycles that change in form as the food is
gathered,
moved backward to the molar
teeth, then broken
down and prepared for
swallowing.

6. tooth bolus
jaw opening
stretch of
elevator
muscles
jaw closing
re-opening of jaw via
stimulation of
periodontal and soft
tissue receptors
NEUROLOGICAL CONTROL
To create precise mandibular
movements, inputs from
various sensory receptors must be
received by the central
nervous system through afferent
nerve fibers. The
brain assimilates and organizes these
inputs and elicits
appropriate motor activities through
the efferent nerve
fibers. These motor activities involve
the contraction of
some muscle groups and the
inhibition of others. Chewing
is a subconscious activity, yet can be
brought to
conscious control at any time

7. MUSCLES OF MASTICATION
The muscles of mastication help in mastication.
All supplied by the mandibular division of the Trigeminal nerve.
Additional muscles of mastication supplied by trigeminal nerve
Anterior belly of digastric
Mylohyoid
Tensor tympani (attaches to the malleus - 1st arch bone - part of the reptilian jaw joint)
Tensor palati

8. PAROTIDEOMASSETERIC FASCIA
 Also referred to as the ‘Masseteric Fascia’.
 A strong layer of fascia derived from the deep
cervical fascia.
 Above it, the lower border of zygomatic arch is
attached.
 Behind, it invests the parotid gland.

9. MASSETER

10.  Arises by thick, tendinous
aponeurosis from zygomatic
process of maxilla and 2/3 of
lower border of zygoma.
 Fibres pass downwards and
backwards.
 Inserted into the angle and
lower half of lateral surface of
ramus of mandible.
 Arises from posterior 2/3 of
lower border and whole of
medial surface of zygomatic
arch.
 Fibres pass downwards and
forwards.
 Inserted into the upper half of
ramus and lateral surface of
coronoid process of mandible.
Superficial Layer Deep Layer
Deep layer is partly concealed in front by superficial layer and behind
by parotid gland.
A thick, quadrilateral muscle and it consists of two
portions:

11. TEMPORAL FASCIA
 Covers the temporalis muscle.
 It is a strong, fibrous investment covered
laterally by auricularis anterior and superiorly
by galea aponeurotica and by part of orbicularis
oculi.
 It consist of two layers:-one of which is inserted
into the lateral and other into medial border of
the arch.
 Between these two layers- a small quantity of fat,
orbital branch of superficial temporal artery and
a filament from zygomatic branch of zygomatic
nerve are present.

12. TEMPORALIS

13.  Arises from whole of the temporal fossa and from
deep surface of temporal fascia.
 Fibres converge as they descend and end in a
tendon which passes which passes deep to the
zygomatic arch.
 Inserted into the medial surface, apex and
anterior border of coronoid process and anterior
border of ramus of mandible nearly as far
forward as last molar teeth.
Broad, radiating muscle situated at the side of the head.

14. LATERAL PTERYGOID

15.  Arises from lower part of
lateral surface of greater
wing of sphenoid and from
infratemporal crest.
 It is active during various
jaw closing movements
only.
 Arises from lateral surface
of lateral pterygoid plate.
 It is active during jaw
opening movements and
protrusion only.
Upper Head Lower Head
Short, thick muscle, conical in form.
Extends horizontally between infratemporalfossa and condyle of mandible.
Arises by two heads:- upper and lower
Fibres pass horizontally backwards and laterally.
Inserted into a depression in front of neck of
condyle of mandible, and into front margin of
articular disc of temporomandibular articulation.
Suited for Protraction, Depression and Contralateral Abduction.

16. MEDIAL PTERYGOID

17.  Arises from medial surface of lateral pterygoid
plate and grooved surface of pyramidal process of
palatine bone.
 Fibres pass downward, lateral and backwards.
 Inserted by strong tendinous lamina, into the
lower and back part of medial surface of ramus
and angle of mandible, as high as the mandibular
foramen.
Thick, quadrilateral muscle.
Principle functions are elevation and lateral positioning
of mandible.

18. ADDITIONAL MUSCLES WHICH ARE
SUPPLIED BY TRIGEMINAL NERVE
Digastric
Geniohyoid
Tensor tympani
Tensor veli palitini

19. DIGASTRIC
 Attachment is at or near lower border of
mandible and near midline.
 Anterior digastric muscle covered by platysma
muscle, beneath lie the mylohyoid and
geniohyoid muscle.
 Mylohyoid branch of mandibular division of fifth
nerve innervates anterior digastric.
 Digastric branch of facial nerve innervates
posterior digastric muscle.

21. GENIOHYOID
 Lies superior to mylohyoid muscle and adjacent
to the midline.
 Arises from mental spine on posterior aspect of
symphysis menti of mandible.
 Inserts on anterior surface of hyoid bone.
 Innervation is from C1 to C2 and hypoglossal
nerve.

23. The tensor tympani, the larger of the two muscles of the tympanic cavity, is
contained in the bony canal above the osseous portion of the auditory tube. Its
role is to dampen sounds, such as those produced from chewing.
When tensed, the action of the muscle is to pull the malleus medially, tensing the tympanic
membrane, damping vibration in the ear ossicles and thereby reducing the amplitude of
sounds.
It arises from the cartilaginous portion of the auditory tube and the adjoining part of the
great wing of the sphenoid, as well as from the osseous canal in which it is contained.
Inserted into the handle (manubrium) of the malleus, near its root.
Passing backward through the canal, it ends in a slender tendon which enters the
tympanic cavity, makes a sharp bend around the extremity of the septum, known as the
processus cochleariformis
TENSOR TYMPANI

25. TENSOR VELI PALITINI
The tensor veli palatini (tensor palati) is a broad, thin, ribbon-like muscle in the head
that tenses the soft palate.
It arises by a flat lamella from the scaphoid fossa at the base of the medial pterygoid
plate, from the spina angularis of the sphenoid and from the lateral wall of the cartilage
of the auditory tube.
The tendon then passes medially and is inserted into the palatine aponeurosis and into
the surface behind the transverse ridge on the horizontal part of the palatine bone.
The tensor veli palatini is innervated by the medial pterygoid nerve, a branch of
mandibular nerve, the third branch of the trigeminal nerve (CN V).
The tensor veli palatini tenses the soft palate and by doing so, assists the levator veli
palatini in elevating the palate to occlude and prevent entry of food into the
nasopharynx during swallowing.

27. MASTICATORY MOVEMENTS

28. IMPORTANCE TO DENTISTS
The knowledge of this system is important in removable
prosthodontics.
Information based on this system was used in the
design and
setting of articulators, and in the design of the dentures
and denture teeth themselves. Today the importance of
jaw movements has become apparent in fixed
prosthodontics,
periodontics, orthodontics, and in the diagnosis and
treatment of pain disorders of the masticatory system.
The most important reason why dentists maintain and
replace missing teeth should be to provide patients with
good masticatory abilities. Therefore, it is important
that dentists know how mastication normally occurs.

29. CLINICAL SIGNIFICANCE
 Horner's syndrome can be produced by lesions of the nasociliary
nerve as it runs with the ophthalmic division.
 Lesions of the ganglion: herpes zoster infection, primary and
metastatic tumors.
 Trigeminal root lesions: adjacent tumors and vascular
malformations, especially acoustic neurinoma and
cholesteatomas. These lesions are prone to produce facial pain
that is often misdiagnosed as tic douloureux or tooth pain.
 Clinically there is atrophy and flaccid paralysis of the muscles of
mastication.