TMJ

Question 1

Describe the TMJ and what it consists of?

Answer 1

Bilateral synovial articulation between the temporal bone and the mandible.

Consists of Joint capsule, articular disc, lateral pterygyroid muscle, stylomandibular ligament , sphenomandibular ligament, mandibular condyles, articular surface of the temporal bone and the temperomandibular ligament.

Question 2

Describe the Joint capsule/ Articular disk

Dif between central and peripheral area?

Answer 2

Capsule- dense fibrous membrane that surrounds the joint, incorporates the articular eminence where it attaches as well as the disc and neck of mandibular condyle

the disk Has upper and lower synovial cavity

Central area avascular, no innervation, however the peripheral part has blood vessels and nerves,
Central area is thinner but dense in consistency compared to the peripheral region which is thicken but is more cushioned.

Question 3

What movement does the joint use?

What muscles are used?

Answer 3

Lower joint part uses rotation upper part- translational. (secondary gliding movement of the jaw) as to move the teeth to masticate.

this is the secondary gliding motion of the jaw as it is opened widely

There is protrusion, retraction, elevation and depression.

Moved by four muscles, temporalis, masseter, and the medial and lateral pterygyoid muscles.

Question 4

Describe the three extra capsular ligaments that stabilise the tmj

Answer 4

Lateral ligament – from the beginning of the articular tubule to the mandibular neck. It is a thickening of the joint capsule, and acts to prevent posterior dislocation of the joint.

Sphenomandibular ligament – Originates from the sphenoid spine, and attaches to the mandible.

Stylomandibular ligament – A thickening of the fascia of the parotid gland. Along with the facial muscles, it supports the weight of the jaw.

bonus: Oto-madnibular logaments connect the malleus to it – discomallear and mallemandibular

Question 5

Name the nerve and blood supply

Answer 5

Innervation - sensory from auriculotemproal and masseteric branches of V3 (mandibular)

Blood provided by branches of ext. carotid (superficial temporal branch)

Question 6

Describe in more detail the articular disk

Structure? Purpose? Innervation?

What about the posterior and anterior portion?

Answer 6

Biconcave structure attaches to the condyle medially and laterally
Upper surface is concavo-convex, under is concave.

Divides joint in to two, these are 2 synovial cavities, upper and lower.
Synovial fluid provided by the synovial membrane.
Central area is avascular, peripheral region has blood vessels and nerves.

Anterior portion splits vertically coinciding with the head of the lateral pterygoid.

Posterior portion also splits vertically . Area between split referred to as retrodiscal tissue

Purpose is to split joint into two and allow movements.

Question 7

Describe the muscles responsible for - Depression

Answer 7

Depression (opening) by gravity and relaxing of muscles that close the jaw.

Eccentricly. Disc moves forward with condyle as it glides forwatd, extending the superior articular surface of the mandibular fossa.

anterior digastric and mylohyoid.

Question 8

Describe the muscles responsible for elevation

Answer 8

masseter,

medial pterygoid pull on the angle of the mandible and temporalis pull up on the coronoid process of the mandible.

Question 9

Describe the muscles responsible for protrusion

Answer 9

lateral pterygoid muscle assised by the medial Pterygoid,

Pulls disc and condyle forward. Within the glenoid fossa and down the articular eminence.

Question 10

Describe the muscles responsible for retraction

Answer 10

Retraction – Geniohyoid and digastric., also the temporalis muscle. Pulling on the coronoid process.