TMJ Histology

Question 1

What are the components of the TMJ?

Answer 1

Condyle

Disc

Ligaments

Question 2

What anatomical structures make up the TMJ?

Answer 2

Temporal bone (articular eminence)

Mandible (condyle)

Article disk

Capsule and supporting ligament

Question 3

What does the articular disk do to the TMJ?

Answer 3

The articular disc separates joint cavity into a superior synovial cavity and an inferior joint cavity. Superior cavity =gliding, inferior cavity = rotational movement when jaw opens initially.

Question 4

How many ligaments support the TMJ?

Answer 4

4 ligaments: Stylomandibular and sphenomandibular
ligaments are accessory and are not directly attached to any part of the joint.

The stylomandibular ligament separates the infratemporal region (anterior) from the
parotid region (posterior), and runs from the styloid process to the angle of the mandible.

The sphenomandibular ligament runs from the spine of the sphenoid bone to the lingula of mandible

Question 5

What is the function of the TMJ?

Answer 5

Allows elevation + depression, protrusion + retraction, and lateral movement.

Question 6

What type of joint is the TMJ?

Answer 6

Synovial joint. Main feature of synovial joint is the synovial fluid which is important for lubrication and protection of the joint. Hinge-like shape (not a pure hinge joint because it allows some gliding motion). Has a disk, 3 ligaments and 4 main muscles that created 5 types of motion.

Question 7

What are the anatomical structures that make up the TMJ?

Answer 7

Temporal bone (articular eminence)

Mandible

Articular disk

Capsule + supporting ligaments

Question 8

What is the clinical significance of the position of the TMJ?

Answer 8

External auditory meatus is right next to the TMJ meaning inflammation of the TMJ can affect hearing

Question 9

What are the histological features of the TMJ?

Answer 9

Bones of the joint consist of 1 condyle, and 2 glenoid fossae and an articular eminence, articular disc, capsular ligament, and joint cavity consisting of synovial fluid.

Question 10

What are the histological features of the mandibular condyle?

Answer 10

From top to bottom consists of: Articular fibrous layer, cartilage layer, calcification zone, compact cortical bone, and spongiosa.

Question 11

What are the histological features of the articular disk in the TMJ?

Answer 11

Dens

Avascular

Tightly packed type 1 collagen fibrous tissue which run in anterio-posterior direction with few elastic fibers, fibroblasts and elongated process

Temporal bone is involved in translational movements and this is the secondary gliding motion of the jaw as it is opened widely.

Question 12

What are the bones of the TMJ?

Answer 12

1 condyle

2 Glenoid fossae, articular eminence

Question 13

What are the features of the articular disc?

Answer 13

TMJs are one of the only synovial joints in the human body with an articular disc.

Disc is composed of fibrocartilagenous tissue and is positioned between the 2 bones forming the TMJ

Question 14

What is the articular disc made of?

Answer 14

Dense, avascular, tightly packed type one collagen fibrous tissue which run in anterio-posterior direction

Few elastic fibers

Fibroblast with elongated process

Chondrocyte with advancing age

Question 15

What is the articular eminence made of?

Answer 15

Formed of spongy bone which covered by thin layer of compact bone.

Covered by thick fibers arranged in 2 layers:

Inner layer: Fibers are at a right angle to the bone surface

Outer layer: Fibers are parallel to bone surface

Question 16

What does the temporal bone do in the TMJ?

Answer 16

Is involved in translational movement; Secondary gliding motion of the jaw as it is opened widely.

It makes the upper surface of the TMJ

Question 17

What is the condyle of the TMJ?

Answer 17

The part of the mandible which makes up the under-surface of the disc. The part of the temporal bone which meets the upper surface of the disk is the glenoid fossa.

Question 18

Where is synovial fluid produced?

Answer 18

Synovial membrane has intimal cells which produce a viscous fluid (plasma, protein, and mucin), containing varying types of cells (monocyte, lymphocyte, sometimes multi0nuclear leukocyte and macrophages)

Question 19

What are the functions of the synovial fluid in the TMJ? (and other joints)

Answer 19

Provide lubrication to joint surfaces to reduce the
wear during joint function.

Provide nutrition to disc , articular surfaces.

Removal of foreign material (phagocytosis)

Question 20

What makes up the temporomandibular ligament?

Answer 20

It has a thickened lateral portion and 2 parts:

Outer oblique portion

Inner horizontal

Question 21

What minor ligaments support the TMJ?

Answer 21

Stylomandibular ligament: Separates the infratemporal region (anterior) from the parotid region (posterior), and runs from the styloid process to the angle of the mandible.

Sphenomandibular ligaments runs from the spine of the sphenoid bone to the lingula of mandible

Question 22

What kind of degenerative changes affect the TMJ?

Answer 22

Age related changes associated with TMJ include; tick fibrous covering of condyle with chondroid changes, synovial folds and villi increase and become fibrotic, osteoporosis of underlying bone, ankylosis, dislocation.

Question 23

How can TMJ dislocation be treated?

Answer 23

Dislocation of TMJ can be treated simply by making patient bite on something then pushing it posteriorly (it is a hinge-joint)