Download File

Muscles of
Mastication
Muscles of mastication:
The muscles of mastication moves the mandible during
mastication and speech. They are:
1) Masseter
2) Temporalis
3) Lateral pterygoid 4) Medial pterygoid
Lateral
pterygoid
Temporalis
Masseter
Medial pterygoid
1)Masseter:
It is a quadrilateral muscle which covers lateral surface of the
Ramus of the mandible.
Origin:
It arises from lower border of Zygomatic arch and from Zygomatic process
of maxilla.
Insertion:
The fibres are inserted into coronoid process and lateral surface of Ramus
of mandible
Zygomatic
arch
Masseter
Nerve supply: Masseteric nerve, a branch of the anterior
division of the Mandibular nerve
Masseteric nerve
Action:
It elevates the mandible to close the mouth and clenches the
teeth
Elevation
Clenching of the teeth
Temporalis: The muscle fills the temporal fossa
Origin:
Arises from temporal fossa, excluding zygomatic bone and from temporal
fascia.
Insertion:
The margins and deep surface of the coronoid process and anterior border
of the ramus of the mandible
Temporal
fascia
Temporalis
Coronoid
process
Nerve supply:
Deep temporal branches from anterior division of the Mandibular
nerve
Temporalis
muscle
Mandibular
nerve
Deep temporal
nerve
Action:
1) It elevates the mandible
2) Posterior fibres retract the potruded mandible:
Retraction
Elevation
Lateral pterygoid:
The muscle has upper head and lower head.
Origin:
Upper head:
It arises from the infratemporal surface and crest of the greater wing of
sphenoid bone
Lower head:
It arises from the
lateral pterygoid plate.
Lower head
Upper head
Insertion:
The fibres get inserted into:
a) Pterygoid fovea on the anterior surface of the neck of the
mandible and to
b) The anterior margin of the articular disc and capsule of the
temporomandibular joint
Articular disc
Capsule of
Temporomandibular joint
Nerve supply:
A branch from anterior division of Mandibular nerve.
Nerve to lateral
pterygoid
Action:
1) Depresses the mandible to open the mouth.
2) The lateral and medial pterygoid acting together protrude the mandible.
3) Alternate contraction of lateral and medial pterygoid produces side to
side movements.
Depression
Medial pterygoid:
This is a quadrilateral muscle having small superficial head and
a large deep head.
Origin:
a) Superficial head: From tuberosity of maxilla and adjoining bone
b) Deep head: From medial surface of lateral pterygoid plate and adjoining
part of palatine bone.
Lateral pterygoid
plate
Deep head
Superficial head
Insertion:
The fibres are inserted into the medial surface of the angle of
the mandible and adjoining part of the ramus of the mandible.
Medial pterygoid muscle
Nerve supply:
Nerve to Medial pterygoid, which is a branch of the main trunk
of the Mandibular nerve
Nerve to Medial
pterygoid
Medial pterygoid
muscle
Action:
1) Elevates the mandible:
2) Helps in protrude the mandible
3) Alternate contraction of Medial and Lateral pterygoid muscles produce side
to side movements
Protrusion
Elevation
TEMPOROMANDIBULAR
JOINT
Variety:
It is a synovial joint of the condylar variety.
Bones forming the joint:
Above:
Mandibular
fossa
Articular tubercle and anterior
articular part of the mandibular
fossa of the temporal bone.
Below:
Head (or) Condyle of the
mandible.
Head of
mandible
Articular tubercle
 Articular surfaces of both bones are covered with fibrocartilage.
 The joint is completely divided by an articular disc into
upper menisco-temporal compartment and a lower meniscomandibular compartment.
Articular disc
Menisco-temporal
compartment
Menisco-mandibular
compartment
Fibro-cartilage
Ligaments:
The joint presents the following ligaments:
1) Capsular ligament with synovial membrane
2) Articular disc
3) Lateral (or) Temporomandibular ligament
4) Accessory ligaments:
a) Sphenomandibular and
b) Stylomandibular ligaments
1) Capsular ligament:
It envelops the joint and presents the following attachments:
Above:
Infront: To the articular tubercle
Squamo-tympanic
fissure
Behind: To the Squamo-tympanic
fissure
And periphery of articular fossa
between them
Below: Attached around the neck of
the mandible
Above the disc the capsule is loose
and below the disc it is tight
Neck of the
mandible
Articular tubercle
Synovial membrane:
It lines the inner aspect of the capsule of each compartment
of the joint, but fails to cover the articular cartilages and
articular disc.
Synovial
membrane
2) Articular disc:
It is an oval plate of fibro-cartilage which caps the head of
mandible and divides the joint cavity into two compartments.
3) Lateral (or) Temporomandibular ligament:
It reinforces and strengthens the lateral part of the
capsular ligament and extends downwards and backwards
from the articular tubercle to the posterolateral aspect of neck
of mandible.
Lateral ligament
Articular
tubercle
Accessory ligaments:
1) Sphenomandibular ligament:
It is situated medial to the capsule and is attached
superiorly to the spine of sphenoid and inferiorly to the
lingula of the mandibular foramen.
Lingula
Spine of
sphenoid
Sphenomandibular
ligament
2) Stylomandibular ligament:
It is formed by the thickening of deep cervical fascia and
extends from the tip of styloid process of temporal bone to
angle of mandible.
Sylomandibular
ligament
Arterial supply:
Branches from superficial temporal and maxillary arteries
Nerve supply:
By Auriculo temporal and Masseteric nerves
Movements:
Movements permitted at the Temporamandibular joints are
1) Protrusion
Protrusion
2) Retraction
3) Depression
4) Elevation
5) Side-side movements
Retraction
(chewing movements)
Elevation
Depression
Muscles producing movements:
Movement Muscles Producing Movement
Protrusion
Retraction
Depression
Lateral pterygoid & Medial pterygoid muscle
Wide opening
Digastric, Geniohyoid, Mylohyoid
Elevation
Side to Side
Movements
Posterior fibres of Temporalis, Masseter & Digastric
Lateral pterygoid muscle
Masseter, Temporalis, Medial pterygoid of both sides
Medial & Lateral pterygoids of both sides acting
alternately
Applied anatomy:
Dislocation of Mandible:
 During excessive opening of the mouth, the head of mandible of one
(or) both sides may slip anteriorly into the infratemporal fossa, as a result
of which there is inability to close the mouth.
 Reduction is done by depressing the jaw with the thumbs placed on
the last molar teeth and at the same time elevating the chin
SUBMANDIBULAR
GLAND
Submandibular salivary gland:
It is one of the three paired salivary glands
Situation:
It is situated in digastric triangle and lodges partly in
submandibular fossa of the mandible upto Mylohyoid line
opposite the molar and premolar teeth.
Mylohyoid line
Submandibular
fossa
It weights about 10-20gms and appears like walnut
Divisions of the gland:
The gland consists of a large superficial part and a small
deep part, both the parts are continuous with each other
around posterior border of Mylohyoid muscle.
Deep part
Mylohyoid
muscle
Superficial part
Superficial part: It presents
Two ends:
1) Anterior end
2) Posterior end
Lateral surface
Three surfaces:
1) Inferior
2) Lateral
3) Medial
Anterior end
Medial surface
Posterior end
Parts:
Anterior end:
it extends upto anterior belly of digastric
Posterior end:
It extends upto Stylomandibular ligament and separates
Sumbandibular from parotid gland.
Anterior belly of
digastric
Surfaces of superficial part:
The surfaces are covered by investing layer of deep cervical
fascia
1) Inferior surface: It presents the following relations:
a) Skin,
b) Platysma,
c) Cervical branch of facial nerve,
d) Deep cervical fascia
f
e) Facial vein,
f) Submandibular lymph node.
e
d
a
b
c
2) Lateral surface: It is related to
a) Submandibular fossa on the mandible
b) Insertion of Medial pterygoid muscle
c) Facial artery
Facial artery
3) Medial surface: It is related to
a. Mylohyoid muscle, nerves and vessels
b. Hyoglossus and Styloglossus
c. Lingual and Hypoglossal
d. Stylohyoid ligament, Glossopharyngeal Nerve(IX)
e. Wall of the pharynx
b
c
a
Deep part :
 It is small in size and lies deep to Mylohyoid and
superficial to Hyoglossus and styloglossus
 Anteriorly it extends upto the posterior end of sublingual
gland
 Posteriorly it continuous with the superficial part around
the posterior border of Mylohyoid.
Styloglossus
Hyoglossus
Mylohyoid
Submandibulat Duct (or) Wharton’s duct:
 It is thin walled and is about 5 cm long and emerges at
the anterior end of the deep part of the gland
Submandibular
duct
Hypoglossal
Lingual nerve nerve
Arterial Supply
Supplied by facial artery
Venous Drainage
Drains into common facial
(or) lingual vein
Lymphatic Drainage
Submandibular lymph nodes
Nerve supply:
The Secreto-motor supply of gland is supplied by both
Parasympathetic and Sympathetic nerves.
Superior salivatory nucleus of Pons

Parasympathetic
Preganglionic
Fibers
Facial Nerve

Chorda Tympani

Lingual Nerve

Submandibular Ganglion
Parasympathetic
Postganglionic
Fibers

Submandibular Gland
Sympathetic fibres:
Sympathetic fibers reach the gland around the facial artery and
convey postganglionic fibers from the superior cervical
ganglion of the sympathetic trunk
Nerve supply:
Preganglionic parasympathetic fibres
------------------ Postganglionic parasympathetic fibres
------------------ Sympathetic fibres
THANK YOU