Tissues + Structures - Joints

Question 1

What is a joint?

Answer 1

Union between bones.

Question 2

What are the type of joints?

Answer 2

1. Fibrous.
2. Cartilaginous.
3. Synovial.

Question 3

Where do fibrous joints occur?

Answer 3

Between bones or cartilages. The surface of bone is joined by fibrous tissue.

Question 4

Example of fibrous joints?

Answer 4

1. Unite the bones of the vault of the skull at the sutures, before they eventually ossify.
2. Unite the lower ends of tibia and fibula - does not ossify.

Question 5

What are the types of cartilaginous joints?

Answer 5

1. Primary.
2. Secondary.

Question 6

What is a primary cartilaginous joint?

Answer 6

Where bone and hyaline cartilage meet.

Question 7

What are examples of primary cartilaginous?

Answer 7

1. Epiphyses.
2. Junction of ribs with their own costal cartilages.

Question 8

Describe how primary cartilaginous joints work?

Answer 8

They are immobile joints that are very strong e.g. bone may fracture but the bone-cartialge interface won’t separate.

Question 9

What is a secondary cartilaginous joint?

Answer 9

Also known as “SYMPHISIS”. Union between bones whose articular surfaces are covered with a thin lamina of hyaline cartilage.

Question 10

What unites hyaline laminae?

Answer 10

Fibrocartilage.

Question 11

What does the joint feature?

Answer 11

Cavity in the fibrocartilage (never lined with synovial membrane) and it contains only tissue fluid e.g. pubic symphisis and joint of sternal angle.

Question 12

What are examples of symphyseal joints?

Answer 12

1. Pubic symphysis.
2. Intervertabral discs - there is a gel in the cavity in the fibrocartilage.
3. Sternal angle (manubrium of sternum and body of sternum).

Question 13

What is movement like in secondary cartilaginous joints?

Answer 13

Limited movement, it depends on the amount of fibrous tissue within them.

Question 14

What are the features of a synovial joint?

Answer 14

1. Articular cavity - in between hyaline cartilage and contains synovial fluid.
2. Hyaline cartilage - bone ends covered in this.
3. Fibrous capsule - surrounds the articular cavity.
4. Synovial membrane - lines the articular capsule.
5. Ligaments - capsule reinforced by the ligaments.
6. Varying degrees of movement.

Question 15

What is the joint capsule called?

Answer 15

Capsular ligament.

Question 16

What happens to this joint as a fetus?

Answer 16

The epiphyseal line gives attachment to the capsule, but as we get older the attachment from the capsule may go past the epiphyseal line and cause the epiphyseal line as an adult to be intracapsular or extracapsular.

Question 17

What does the synovial membrane do?

Answer 17

Lines the capsule and invests all non-articulating surfaces within the joint i.e. it is attached round the articular margin of each bone.

Question 18

What do some cells of the synovial membrane do?

Answer 18

Secrete hyaluronic acid derivative - this is responsible for the viscosity of the fluid and to maintain lubrication.

Question 19

What can the synovial fluid do?

Answer 19

Change its viscosity depending on the movement:
1. Thinner with rapid movement.
2. Thicker with slow movement.

Question 20

How much synovial fluid is in a synovial joint?

Answer 20

Minimal - knee contains about 0.5ml. But injury and infection can cause it to increase (effusions).

Question 21

What is it when a joint is “close-packed”?

Answer 21

The surfaces of each bone have maximal contact with each other as possible and the ligaments are at their tightest.

Question 22

What is it when a joint is “loose-packed”?

Answer 22

The surfaces of each bone aren’t touching as much and the capsule is looser and the ligaments aren’t tight.

Question 23

What is the blood supply to hyaline cartilage?

Answer 23

No blood supply.

Question 24

Where does the blood vessel to the long bone shaft come from?

Answer 24

Branches from the main artery of the particular segment and as the bone gets longer the artery is carried obliquely away from the growing end of the bone.

Question 25

What is the metaphysis?

Answer 25

The area of the end of the shaft with the epiphyseal plate of cartilage.

Question 26

What is blood supply in the metaphsyis as children?

Answer 26

Terminal branches of the nutrient arteries of the shaft.

Question 27

What supplies the synovial membrane?

Answer 27

Vasacular plexus that surrounds the epiphysis and sens branches to joint structures.

Question 28

What is the circulus vasculosus?

Answer 28

Blood vessels of synovial membrane that lay between the capsule and synovial membrane and attach at the epiphyseal line.

Question 29

What happens to the blood supply when we get older?

Answer 29

Vascular communications are established and the metaphysis contains no end arteries and is not at risk of infection like osteomyelitis.

Question 30

What is the nerve supply of the articular capsule?

Answer 30

Afferent nerve endins (including myelinated pain fibres).

Question 31

Does synovial membrane contain pain fibres?

Answer 31

Few pain fibres .

Question 32

Does articular cartilage contain pain fibres?

Answer 32

None - this means that joint pain is poorly localised.

Question 33

What is hilton’s law?

Answer 33

The motor nerve to a muscle tends to give a branch of supply to the joint which the muscle moves and another branch to the skin over the joint.

Question 34

What do ligaments do in joints?

Answer 34

Preventing over-movement and guarding against sudden accidental stresses. Have no help against continuous stress on joints.

Question 35

What is the most important structure in maintaining stability in joints?

Answer 35

Muscles.