synovium

Question 1

Synovium definition

Answer 1

A soft membrane (loose vascular CT) that lines synovial joints, tendon sheaths and bursae

Question 2

Location of synovial membranes

Answer 2

Locations of synovial membranes:
Synovial Joints
- Lining joint capsule (just capsule not articular surface)
- Usually attached to articular margins
Bursa = decreases friction b/w two different things
- Sac lined with synovial membrane containing synovial fluid
Tendon synovial sheaths
- Bursae that have tendons embedded in them

Question 3

Synovial membrane: structure and properties

Answer 3

• Vascular (a lot of blood supply) connective tissue with folds and villi (finger-like projections): increases membrane surface area (allows for more release and uptake of synovial fluid) and promotes distribution of synovial fluid
• Inner cellular layer with 2 types of cells
  
  • Cells that produce hyaluronic acid (a type of GAG) = increase viscosity of synovial fluid
  • Cells that phagocytose debris
• Outer vascular/fibrous layer thin, loose vascular connective tissue
  
  • Contains varying amounts of adipose tissue
    Function: secrete and absorb synovial fluid = constant flow of new synovial fluid

Question 4

Synovial Fluid: Structure, properties, function

Answer 4

• plasma-like fluid
• contains 1/3 protein content of plasma
• contains hyaluronic acid (increases viscosity)
  Property:
• is thixotropic (changes w/ movt)
• viscosity decreases w/ higher temp, faster joint velocity, higher pH
  Functions:
• lubricates joint to reduce friction: increases joint efficiency, reduces erosion of articular surfaces
• provides nutrition and removes waste products of metabolism
• provides shock absorption

Question 5

Changes to synovial membrane in inflammatory joint disease e.g. rheumatoid arthritis

Answer 5

during this disease the SM:

• becomes more vascular
• becomes more permeable
• accumulates “inflammatory” cells that coat the SM when they die
• this leads to: LOWER hyaluronic acid production (decreased viscosity) = less protective, LOWER phagocytic activity –> more debris that coat SM, loses thixotropic property (less protection), increased volume = joint swelling,

Question 6

Consequences of changes in synovial membrane and fluid due to inflammation: A summary

Answer 6

• Because: Synovial fluid becomes less viscous and less thixotropic:
• Consequence: loss of protective function of synovial fluid …so….joint surfaces are more susceptible to damage
• Because: Increased risk of clotting in synovial fluid
• Consequence: loss of lubricating function (more abrasion) → joint surfaces are more susceptible to damage
• Because: of the joint swelling stretching the joint capsule and associated ligaments occurs
• Consequence: the affected joint is less stable (as the joint surfaces are being pulled apart a little bit = end up with slightly less congruity of joints)