Joints, Synovial Fluid and Cartilage

Question 1

Give the 3 types of joints along with their very basic roles

(what are these joints?
What is their basic structure?)

Answer 1

Fibrous
-Articulating bones joined by fibrous tissue, often interlocking along a wavy line.

Cartilaginous
-Articulating bones united by fibrocartilage or hyaline cartilage

Synovial
-Two bones separated by a characteristic joint cavity containing synovial fluid

Question 2

Give 3 types of fibrous joint

Answer 2

Sutures
(cranial sutures)

Gomphosis
(dento-alveolar joint/ periodontal ligament)

Syndesmosis
(interosseous membranes)

Question 3

Give the two types of cartilaginous joint

Answer 3

Primary joint

Question 4

Give the two types of cartilaginous joints

Answer 4

Primary cartilaginous

• (Synchondrosis)
• Hyaline
• Long bones

Secondary Cartilaginous

• (Symphysis)
• Fibrocartilaginous disc
• Vertebrae and more axis structures

Question 5

What structure in a synovial joint produces synovial fluid?

Answer 5

Synovial membrane

Question 6

Try to name as many synovial joints as you can.
Give an example for each

(there are 6)

Answer 6

Plane
-acromioclavicular joint

Condylar/ Condyloid
-Metacarpophalangeal joint

Hinge
-elbow joint

Saddle
-carpometacarpal joint

Pivot
-atlanto-axial joint

Ball and socket
- hip joint

Question 7

What 3 factors combine to give a joint stability?

Answer 7

Shape of articulating surfaces

Capsule and ligament holding in place

Muscles

Question 8

Describe the type of cells and what they produce in the superficial/ tangential layer of articular cartilage.

How is collagen arranged in this layer and why?

Answer 8

Cells:
-Flattened chondrocytes

Produce:
-Collagen and glycoproteins like lubricin

Arrangement of collagen fibres
-Horizontal to hold structure against sheering forces

Question 9

What does lubricin do?

Answer 9

Acts as lubricant in the joint

Question 10

Describe the type of cells and what they produce in the transitional layer of articular cartilage.

How is collagen arranged in this layer?

Answer 10

Cells:
-Round chondrocytes

Produce:
-Proteoglycans such as aggrecan

Arrangement of collagen fibres:
-Oblique / diagonally

Question 11

What does aggrecan do?

Answer 11

Attracts water easily

Water very incompressible and makes the cartilage more strong

Question 12

What is the arrangement of collagen fibres in the deep layer of articular cartilage?

Answer 12

Horizontal

Question 13

Cartilage is a unique structure in that it is a tissue that lacks which 3 essentials?

Answer 13

Avascular
Aneural
Alymphatic

Question 14

What is synovium?

What cells make it up?

What does it do?

Answer 14

Synovial fluid produced by synovial membrane (synovium)

Synoviocytes producing fluid

Rich capillary network -> direct exchange of oxygen, carbon dioxide and metabolites between blood and synovial fluid

Question 15

What are the two types of synoviocytes?

What do each type of synoviocytes do?

Answer 15

Type A are mainly phagocytic and pinocytic;

Type B are chiefly synthesizers.

Question 16

What makes up synovial fluid?

Answer 16

Hyaluronic acid

Lubricin

Fluid component from blood plasma

Question 17

What are the 3 functions of synovial fluid?

Answer 17

Nutrition of cartilage

Removal of waste products

Lubrication

Question 18

What are the 3 types of lubrication?

Answer 18

Boundary

Hydrodynamic

Weeping

Question 19

What are bursae?

very basically

Answer 19

Synovial membranes which are fluid filled.

Reduce friction

Separate from the actual joint and lie under tendons etc

Question 20

How do joints change with age?

Very basically in terms of synovial fluid and cartilage

Answer 20

Viscosity of synovial fluid increases

• Slower joint movements
• Reduced lubrication

Water content of cartilage decreases
-Reduced shock absorption

All this leads to less protection of articular surfaces and increased risk of damage