Anatomy of the mandible, muscles of mastication and the temporomandibular joint (TMJ)

1. MANDIBLE
MUSCLES OF MASTICATION
AND
TEMPOROMANDIBULAR JOINT
ESSAM ELDIN ABDELHADY SALAMA
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2. Mandible
It consists of a horseshoe-
shaped body and a pair of
rami
The body meets the
ramus on each side of the
angle of the mandible
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3. BODY
Horizontally placed, is
composed of two halves fused
at the middle
On its external surface;
Has the symphysis menti on
the midline indicates fusion of
its halves during its
development.
Mental foramen is seen below
the 2nd premolar tooth ,
transmits terminal branches of
inferior alveolar nerve and
vessels.
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4. On the internal surface
Mental spines are found in the
midline giving attachment to
genioglossus above and
geniohyoid below
The mylohyoid line; is seen as
an oblique ridge runs
backward and laterally from
the area of mental spines to
the area below and behind the
3rd molar tooth
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5. The submandibular fossa; for
the superficial part of the
submandibular salivary gland
Sublingual fossa; for Sublingual
salivary gland
Lies in relation to the mylohyoid
line;
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6. The upper border of the
body is called the alveolar
border; contains sockets of
teeth.
The lower border is called
the base it contains;
The digastric fossa on either
sides of the symphysis menti
for the anterior bellis of
digastric muscles.
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7. THE RAMUS
Is vertically placed;
it has an anterior coronoid
process and
posterior condyloid process
(head)
the two processes are
separated by the
mandibular notch
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8. THE RAMUS
The lateral surface;
Contains rough area for the
attachment of masseter
muscle
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9. THE RAMUS
The medial surface;
lies the mandibular foramen for
inferior alveolar nerve and
vessels.
Anterior to the foramen is a
projection of bone the lingual for
attachment of the
sphenomandibular ligament
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10. The mandibular foramen leads
into the mandibular canal that
connected to the mental
foramen
The incisive canal is a
continuation forward of the
mandibular canal below the
incisor teeth
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11. THE RAMUS
The medial surface;
Lies the attachment of medial
pterygoid muscle near the angle
The coronoid process receives
on its medial surface the
attachment of the temporalis
muscle
Below the head is a short neck;
anteriorly gives attachment to
lateral pterygoid muscle.
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12. MUSCLES OF MASTICATION
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13. Muscles of mastication
1. Temporalis.
2. Masseter.
3. Lateral pterygoid.
4. Medial pterygoid.
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14. Temporalis
Origin: Floor of temporal fossa
and deep surface of temporal
fascia.
Insertion: Coronoid process and
anterior border of ramus of
mandible.
Nerve supply: Deep temporal
nerves (from and the anterior
division of mandibular
nerve).
Action: Elevation and retraction
of the mandible.
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15. Masseter
Origin: Lower border and inner
surface of the zygomatic
arch.
Insertion: Lateral aspect of the
ramus of the mandible.
Nerve supply: anterior division
of the mandibular nerve.
Action: Elevation and
protraction of the mandible.
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16. Lateral pterygoid
Origin:
Upper head: from the infratemporal
surface of the greater wing of
sphenoid bone.
Lower head: from the lateral surface
of the lateral pterygoid plate.
Insertion:
anterior aspect of the neck of the
mandible and the articular disc
of the temporo-mandibular joint.
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17. Lateral pterygoid
Nerve supply: anterior division
of the mandibular nerve.
Action: pulls the head of
mandible forward during
opening of the mouth (helps
in depression of mandible),
protracts the mandible and
side to side moves it
(chewing).
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18. Medial pterygoid
Origin:
Superficial head: from the
maxillary tuberosity.
Deep head: from the medial
surface of the lateral
pterygoid plate.
Insertion:
medial surface of the angle of
the mandible.
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19. Medial pterygoid
Nerve supply:
Main trunk of the mandibular nerve.
Action:
helps in elevation of mandible,
protraction of the mandible and
side to side movement (chewing).
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20. TEMPOROMANDIBULAR JOINT
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21. TEMPOROMANDIBULAR JOINT
It is a condylar synovial joint
Articulation
Articular surface and tubercle of
the temporal bone
Head of the mandible
The joint cavity is divided into
upper and lower parts by an
articular disc
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22. TEMPOROMANDIBULAR JOINT
Capsule
Gives attachment to the margins
of the articular disc and lined by
synovial membrane
Articular disc
Its upper surface is
concavoconvex to fit into the
articular tubercle and fossa
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23. Accessory ligaments
Lateral ligament:
between the tubercle of the
root of zygoma and lateral
surface of the neck of
mandible.
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24. Accessory ligaments
Sphenomandibular ligament’
From the spine of sphenoid to the
lingual of mandible
Related laterally to the lateral
pterygoid, auriculotemporal nerve,
maxillary artery, inferior alveolar nerve,
and inferior alveolar vessels.
Related medially to the chorda tympani
and medial pterygoid
It is derivative of the first pharangyial
arch
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25. Accessory ligaments
Stylomandibular ligament
From the tip of the styloid
process to posterior border of
ramus and angle of mandible
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26. Arterial supply
Twigs from superficial temporal
and maxillary arteries
Nerve supply
Auriculotemporal nerve and
nerve to masseter
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27. MOVEMENTS
Depression; to open the
mouth ;
Lateral pterygoid on both sides
, helped by digastric,
mylohyoid and geniohyoid
Elevation; to close the mouth;
Masseter, temporalis, and
medial pterygoid on both sides
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28. MOVEMENTS
Protrusion;
Lateral and medial pterygoid
on both sides.
Retraction
Posterior fibers of temporalis
on both sides.
Side to side (chewing);
Lateral and medial pterygoid
on both sides acting
alternately
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29. On opening the mouth
the head of the
mandible first rotates on
the articular disc at the
same time forward
displacement of the disc
on the articular tubercle
On closing the mouth
the reverse occurs.
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