Joints, Synovial Fluid and Cartilage

Question 1

Name the three structural classifications of joints?

Answer 1

• Fibrous
• Cartilaginous
• Synovial

Question 2

Give three examples of fibrous joints

Answer 2

• Cranial sutures
• Periodontal ligament
• Interosseus membranes

Question 3

Give the two types of cartilaginous joints and the difference between them

Answer 3

• Primary:/Synchondrosis only contains hyaline cartilage

- Secondary/Symphysis: contains hyaline and fibrocartilage

Question 4

Give examples of where cartilaginous joints are found

Answer 4

• Primary: Epiphyseal growth plate

- Secondary: Intervertebral disc

Question 5

What are the common features of synovial joint?

Answer 5

• Synovial cavity (fluid-filled)
• Articular cartilage
• Fibrous capsule
• Synovial membrane
• May also contain: articular discs, ligaments and bursae

Question 6

Name the common types of synovial joints

Answer 6

• Plane
• Hinge
• Pivot
• Condylar
• Saddle
• Ball and Socket

Question 7

Which factors contribute to joint stability?

Answer 7

• Shape of articulating surfaces
• Capsules and ligaments
• Muscles

Question 8

Name the features of Articular (hyaline) cartilage

Answer 8

• Superficial layer: contains flattened chondrocytes that produce collagen and glycoproteins
• Transitional layer: contains round chondrocytes that produce proteoglycans
• Changes in collagen orientation from superficial to deep
• > 75% water (incompressible)

Question 9

What are glycoproteins?

Answer 9

Proteins to which oligosaccharide chains are attached e.g. lubricin

Question 10

What are proteoglycans?

Answer 10

Proteins that are heavily glycosylated e.g. aggrecan

Question 11

What are glycosaminoglycans (GAGs)?

Answer 11

Long unbranched polysaccharides, which are highly polar and thus attract water e.g. hyaluronic acid

Question 12

Which structures does cartilage not contain?

Answer 12

• Blood vessels
• Nerves
• Lymphatics

Question 13

Which structure produces synovial fluid?

Answer 13

Synovial membrane - synoviocytes

Question 14

How do oxygen, CO2 and metabolites reach the synovium?

Answer 14

Direct exchange between blood and the synovial fluid

Question 15

What are the two types of synoviocytes and how do they differ?

Answer 15

• Type A: look like macrophages, remove debris and contribute to synovial fluid production
• Type B: like fibroblasts and are the main producers of synovial fluid

Question 16

What are the main components of synovial fluid?

Answer 16

• Viscous fluid
• Contains hyaluronic acid and lubricin
• Fluid component from plasma
• Small volumes
• Rapid turnover

Question 17

What are the functions of synovial fluid?

Answer 17

• Nutrition of cartilage
• Removal of waste products
• Lubrication

Question 18

What are the three mechanisms of lubrication of joints?

Answer 18

• Boundary: glycoproteins bind to receptors on articular surfaces to form a thin film
• Hydrodynamic: surfaces are kept apart by liquid pressure
• Weeping: fluid present in the cartilage is squeezed into the synovial cartilage to increase fluid volume

Question 19

What are bursae and what is their function?

Answer 19

• Fluid filled sacs in the joint

- Reduce friction

Question 20

What happens to the joints as part of the ageing process?

Answer 20

• Viscosity of the synovial fluid increases (slower movements and reduced lubrication)
• Water content of cartilage decreases (reduced shock absorption)
• Less protection of articular surfaces and increased risk of damage