Joints, Synovial Fluid and Cartilage

Question 1

What different types of joint exist?

Answer 1

Fibrous
Cartilaginous
Synovial

Question 2

What connects bone in fibrous joints?

Answer 2

Collagen fibres (dense fibrous connective tissue)

Has a high tensile strength making it hard to pull the bones apart

Question 3

What connects bone in cartilaginous joints?

Answer 3

Cartilage

Question 4

Give some examples of a fibrous joint (3)

Answer 4

Cranial sutures
Interosseous membranes
Periodontal ligaments (teeth)

Question 5

What types of cartilaginous joints exist and give some examples

Answer 5

Primary joint - hyaline

Secondary joint - more in the axis

Question 6

What is the function of a synovial membrane?

Answer 6

To produce synovial fluid and form the synovial cavity

Question 7

What surrounds the synovial membrane?

Answer 7

Fibrous capsule

Question 8

What are the different types of synovial joint?

Answer 8

Planar
Condylar
Hinge
Saddle
Pivot
Ball and Socket

Question 9

How can joint stability be worked out?

Answer 9

Shape of articulating surfaces
Capsule and ligaments holding in place
Muscles

Question 10

What types of cartilage are there?

Answer 10

Hyaline cartilage

Fibrocartilage

Question 11

What cartilages are there in the knee joint?

Answer 11

Meniscus - fibrous cartilage

Hyaline cartilage on kneecap

Question 12

Explain the layers in articular (hyaline) cartilage

Answer 12

Superficial/tangential layer - flattened chondrocytes that produce collagen and glycoproteins
Transitional layer - round chondrocytes that produce proteoglycans such as aggrecan
Change in collagen orientation from superficial to deep layers
>75% water
Glycoproteins like lubricin act as lubricators of the joint

Question 13

What does cartilage lack?

Answer 13

Blood supply
Nervous supply
Lymphatic drainage

Avascular
Aneural
Alymphatic

Question 14

What is synovium?

Answer 14

Lines the inner of the capsule of the synovial joint
Made up of synoviocytes which produce the fluid
Has a rich capillary network and no epithelial lining

There is a direct exchange of oxygen, carbon dioxide and metabolites between blood and synovial fluid

Question 15

What types of synoviocytes exist and what are their functions?

Answer 15

Type A - look like macrophages, remove debris

Type B - production of synovial fluid

Question 16

What are the characteristics of synovial fluid?

Answer 16

Viscous fluid
Hyaluronic acid and lubricin
Fluid component (from blood plasma)
Small volumes
Rapid turnover

Question 17

What are the functions of the synovial fluid?

Answer 17

Nutrition of cartilage (articular cartilage/minisci)
Removal of waste products
Lubrication causing there to be less friction and therefore less wear to the joint

Question 18

What elements are there to the lubrication of a synovial joint?

Answer 18

Boundary - glycoproteins such a lubricin bind to receptors on the articular surfaces to form a thin film
Hydrodynamic - surfaces are kept apart by liquid pressure. Viscosity changes with load and the velocity of movement
Weeping - fluid that is present in the cartilage is squeezed out into the synovial cavity to increase fluid volume

Question 19

How is lubrication measured?

Answer 19

Co-efficient of friction

Question 20

What are bursae?

Answer 20

Fluid filled synovial membrane sacs which surround joints which reduce friction

Question 21

What happens to synovial joints during the ageing process?

Answer 21

Viscosity of synovial fluid increases due to slower joint movements and reduced lubrication

The water content of cartilage decreases causing reduced shock absorption

Less protection of articular surfaces and increased risk of damage