Joints

Question 1

What is craniostynosis?

Answer 1

Premature fusion of the sutures of the skull leading to deformities of shape and growth within the structure.

Question 2

How many discrete layers are present in a suture?

Answer 2

5

2 osteogenic layers, 2 periosteal layers and a loose connective tissue layer in the centre.

Question 3

Where within a bone of the skull is the oldest bone?

Answer 3

Centrally as this is displaced from the outsides by osteogenic zones.

Question 4

Where are synchondrosis found in the skull?

Answer 4

In the skull base.

Question 5

How does a synchondrosis differ from a suture?

Answer 5

It contains layers of non-articular hyaline cartilage which separate the areas of ossification.

Question 6

How many layers in a synchondrosis?

Answer 6

7

It is the equivalent of 2 epiphyseal growth plates separated by a resting zone.

Question 7

What pattern of growth do calvarial bones show? What is this an alternative too?

Answer 7

Neural growth. This means that it is accelerated initially and then reduces as we approach the 3rd decade.
This is an alternative to somatic growth which slows and then shows acceleration during puberty.

Question 8

How fast do bones of the head grow?

Answer 8

The calvarial bones and the orbit grow at a neural rate because pressure from the internal neural structures is exerted on them.
The bones of the lower face grow at a somatic rate and show a large spurt during puberty.

Question 9

What changes occur to the bones of the calvarial besides increase in size?

Answer 9

Reduced curvature as the brain enlarges,

Question 10

What is cortical drift?

Answer 10

This is a process in which bone is deposited on one surface and reabsorbed from the other which leads to migration of the bone in the direction of bone deposition,

Question 11

Describe how the palate enlarges as the skull grows.

Answer 11

There is deposition of bone medially on the palate, however migration cannot occur due to the medial palatine suture and so this forces the whole structure to enlarge. The same occurs anterioposteriorly due to posterior migration being prevented by the pterygoid plate.

Question 12

What movements are achieved at the Temporomandibular Joint?

Answer 12

Rotation and anterior translation

Question 13

List the vessels which supply blood to the TMJ

Answer 13

Maxillary, Superficial Temporal, Middle Meningeal

Question 14

Where does venous blood from the TMJ drain?

Answer 14

Pterygoid venous plexus and superfifcial temporal vein

Question 15

Which nerves supply sensation to the TMJ.

Answer 15

Auriculotemporal (main)
Deep Temporal
Massesteric

Question 16

What are the thickenings of the capsular ligament of the TMJ?

Answer 16

Inner Horizontal Part - protects retrodiscoid tissue

Outer Oblique Part - stretches with opening of the jaw and provides the 2nd centre for rotation

Question 17

What structure produces translation of the head of mandible anteriorly?

Answer 17

On opening of the jaw with rotation the outer oblique part of the capsular ligament becomes stretched and provides a new centre for rotation which causes translation of the mandibular head onto the anterior eminence.

Question 18

What is the function of the Inner Horizontal Part of the capsular ligament?

Answer 18

This protects the highly neurovascular tissue found in the retrodiscoid space.

Question 19

Name the accessory ligaments of the TMJ and their functions?

Answer 19

Stylomandibular ligament - prevents excessive translation of the mandible which could lead to dislocation.
Sphenomandibular ligament - assists. With translation of the head of the mandible and prevents excessive posterior displacement.

Question 20

Which structure associated with TMJ may interfere with Inferior Alveolar Nerve Block

Answer 20

Stylomandibular Ligament - the nerve runs on one side of this ligament so if the wrong space is occupied by the needle then a fully functional block may not be Provided due to insufficient anaesthetic reaching the nerve,

Question 21

Describe the structure of the articular disc.

Answer 21

The articular disc has both anterior and posterior thickenings. The anterior of the disc is continuous with the capsular ligament and then superior head of lateral pterygoid. The posterior has both superior (elastic) lamina and inferior (collagenous) lamina.

Question 22

Describe the joint space of the TMJ

Answer 22

This is split into two discrete areas - superior and inferior which are unable to communicate.

Question 23

What role does lateral pterygoid have in movement of the mandible?

Answer 23

Superior head - manipulation of the articular disc during mouth closing.
Inferior head - assists with opening the jaw,

Question 24

In a coronal section, describe the articular disc of the TMJ,

Answer 24

The articular disc is highly curved around the head of the mandible and is held here tightly by the medial and lateral discoid ligaments.

Question 25

Which part of the TMJ joint cavity permits each movement?

Answer 25

Inferior - rotation

Superior - translation. This is possible because the capsular ligament has relative laxity,

Question 26

Name the muscles involved in opening the mouth,

Answer 26

Mylohyoid, digastric, Inferior Head of lateral pterygoid,

Question 27

Name the muscles involved in closing the mouth.

Answer 27

Muscles of mastication - particularly temporalis,

Question 28

At rest, which part of the articular disc does the mandibular head rest against? How is this achieved?

Answer 28

Posterior thickening

Tension in superior belly of lateral pterygoid holds the disc in place.

Question 29

During opening of the mouth, describe the changes within. The TMJ,

Answer 29

When mouth opening occurs, the contraction of inferior head of lateral pterygoid moves the mandibular head up against the anterior thickening of the articular disc. This is then translated anteriorly with the mandible which produces tension in the elastic, superior retrodiscoid lamina.