1. TMJ and Muscles of Mastication
Dr Rania Gabr

2. Objectives Identify the parts of the mandible.
Know the type and formation of temporomandibular joint.
Understand the attachment of the capsule and ligaments of the temporomandibular joint.
Explain the mechanism of movements taking place at temporomandibular joint.
Define the stability factors of the joint.
Explain the muscles of mastication with their origin, insertion, nerve supply and actions.
Discuss maxillary artery.

3. Gross Anatomy This is a synovial joint of condylar variety.
COMPONENTS:
Mandibular condyles
Articular surfaces of Temporal bone
Capsule
Articular disc
Ligaments

4. ARTICULAR SURFACES- A. Upper part - a) Articular eminence,
b) ant. part of mandibular fossa.
B. Inferior surface -
head of the mandible.

5. ARTICULAR DISC (MENISCUS)
Fibro cartilaginous tissues
Disc divides the compartment into 2:
Upper formed by Temporal bone and articular disc (Menisco temporal)
Lower formed by mandible and articular disc (Menisco mandibular)

6. CAPSULE Fibrous membrane that surrounds the joint
Covers the joint from all around
Thin above the disc and thick below it
Encloses the disc
Attaches above: to the margins of the mandibular fossa
Attaches below: to the neck of the mandible
The inner aspect of capsule attaches to disc
Above disc – capsule loose
Below disc - tight

8. LIGAMENTS Major Ligaments Temporomandibular ligament Lateral ligament
Minor Ligaments
Stylo mandibular ligament
Spheno mandibular ligament

10. Movements
Elevation
Depression
Retraction
Protraction
Side to side

11. Movements Side to side – grinding movements
Mandible is alternately protracted and retracted with the two sides moving in opposite directions so that one side is protracted while the other is retracted
Actions combined with elevation and depression, rhythmically and alternately.
Opening of the jaw (depression) ,is primarily passive or gravity assisted.

12. MUSCLES
Messeter
Temporalis
Medial pterygoid
Lateral pterygoid

13. INNERVATION TRIGEMINAL NERVE: Mandibular div. SENSORY
Auriculo temporal nerve: from the posterior division of the mandibular nerve
Messeteric nerve: from the anterior division of the mandibular nerve
MOTOR
Mandibular division of trigeminal nerve

14. Temporalis
Its a fan shaped muscle Covered by temporal fascia Origin: Medial wall of the temporal fossa and temporal fascia Insertion: Anterior margin of coronoid process and anterior border of the ramus of mandible Nerve supply: Deep temporal branch of anterior division of mandibular nerve

15. TEMPORAL FASCIA Attachment: Above: Superior temporal line Below:
It splits into 2 layers and insert into respective borders of zygomatic bone

16. ACTION:
ANT - Elevation of the
mandible
POST – Retraction of mandible
Middle fibres - Oblique
Anterior fibres – vertical
Posterior fibres - Horizontal

17. Masseter It is quadrilateral in shape.
Can be palpated in living subjects on clenching the teeth
It consists of 2 layers :
Superficial and deep.
Origin:
Lower margin and deep aspect of zygomatic arch
Insertion:
Lateral surface of ramus and coronoid process of mandible

18. Protracts the mandible
Nerve supply:
Masseteric nerve from the anterior division of
mandibular nerve.
Action:
Elevates the mandible
Superficial fibres:
Protracts the mandible

19. Pterygoid muscles There are medial and lateral pterygoid muscles.
They extend from the pterygoid plates and insert in the mandible.
Lateral pterygoid
Partotid duct
Buccinator
Medial pterygoid

20. Lateral pterygoid It is a short, thick muscle consisting of two parts
I) Upper head
II) Lower head
Origin:
Upper head: Infratemporal surface of greater wing of sphenoid
Lower head: Lateral surface of the lateral pterygoid plate
Insertion: Pterygoid fovea (depression on the front of the neck of the mandible)
Capsule of TMJ
Upper head
Lower head
Some fibres of upper head may insert
in the capsule of tempero-mandibular joint

21. Lat. Pterygoid - Attachment
Upper head
Infra temporal
Sufrace of greater
wing of sphenoid
Lower head
Lateral surface of
lateral pterygoid plate
Nerve supply: Anterior division of
mandibular nerve
Action: opening of mouth (Depression of mandible) by pulling forward the
head of mandible. Upper head – chewing, Lower head – protrusion.
Side to side movements: combined action of medial and lateral pterygoid

22. Medial pterygoid
It consists of large deep head and small superficial head.
Origin:
Deep head: Arises from the medial surface of lat.pterygoid plate
Superficial head:
Tuberosity of maxilla
Insertion:
Medial surface of ramus and angle of mandible.
Nerve supply: Branch from the trunk of mandibular nerve
Deep head
Superficial head

23. Deep fibres
Superficial
fibres
Action: Elevation of mandible. Together with lateral pterygoid, it helps in side to side chewing movement.

24. VASCULARISATION Branches of External Carotid Artery
Superficial temporal artery
Deep auricular artery
Anterior tympanic artery
Ascending pharyngeal artery
Maxillary artery

25. VASCULARISATION
The Blood supply to TMJ is only Superficial, i.e there is no blood supply inside the capsule
TMJ takes its nourishment from Synovial fluid

26. Clinical Anatomy Trismus:
Tonic spasm of both masseters is the characteristic symptom of tetanus which produces “lock jaw”

28. Clinical Anatomy (contd...)
Submasseteric space infection:
Infection around 3rd molar tooth may seep into the space between the attachment of masseter with mandible which leads to visible swelling and limitation of jaw movements

29. Clinical Anatomy (contd...)
Paralysis of lateral pterygoid muscles causes the jaw to deviate towards the paralysed side on opening the mouth as a result of action of normal muscle.