Joints, synovial fluid and cartilage Flashcards
What are the three types of joints?
Fibrous
Cartilagenous
Synovial
Where do you find fibrous joints?
In the peridontal ligament
In the cranial sutures
In the interosseus membranes
What are the different types of cartilaginous joints?
Primary joint - only hyaline cartliage, these are also known as synchondrosis - found in the epiphyseal groath plate of long bones
Secondary joint - contains hyaline and fibrocartilage, also known as symphysis - found in the intervertebral disks
What are secondary cartilaginous joints?
What are the components of the synovial joint?
Contains:
Synovial cavity
Articular cartilage
Fibrous capsule
Synovial membrane
May also contain -
articular discs, ligaments and bursae
What are the different types of synovial joints?
Plane - these are the facet joints in the vertebral column
Hinge
Pivot - radioulnar joint
Condylar - atlanto occipital joint
Saddle (between the trapezium and the 1sr metacarpal)
Ball and socket
What does joint stability depend on?
Shape of articulating surfaces
Capsule and ligaments
Muscles
Why is the shoulder more likely to dislocate than the hip?
Shoulder joint is more shallow
What cartilage is present in synovial joints?
Hyaline cartilage and fibrocartilage
Hyaline cartilgae is found in the articulating surfaces
What is found in the superficial layer of articular cartilage (hyaline cartilage)?
Flattened chondrocytes that produce collagen and glycoproteins (such as lubricin)
What is found in the transitional layer of articular cartilage?
Round chondrocytes that produce proteoglycans such as aggrecan
What percentage of articular cartilage is water?
Over 75% is water - making the carilage incompressible
What is the action of aggrecan?
Attracts water
What are glycoproteins?
Oligosaccharide chains are attached to proteins - more a protein than a carbohydrate
Example is lubricin
What is a proteoglycan?
Proteins that are heavily glycosylated - a protein core to which one or more GAGs attach - tend to be more carb than protien
What are GAG’s?
•Glycosaminoglycans or GAGs (e.g. hyaluronic acid): long unbranched polysaccharides, which are highly polar and thus attract water
Cartilage is avascular - aneural and alymphatic - how does it recieve nutrients and remove waste products?
Synovial fluid produced by synovial membrane (synovium)
What produces synovial fluid?
synoviocytes of the synovium
What is the structure of the synovium?
Rich capillary network - no epithelial lining
What is the movement of nutrients in and out of the synovial fluid?
→Direct exchange of oxygen, carbon dioxide & metabolites between blood & synovial fluid
What are the types of synoviocytes?
Type A and Type B
What is the function of synoviocytes Type A?
Remove debris - contribute to synovial fluid produciton
They also look like macrophages
What is the function of synoviocytes type B?
They are the main producer of synovial fluid and are fibroblast like
What are the componentes of synovial fluid?
- Viscous fluid
- Hyaluronic acid & lubricin
- Fluid component (from blood plasma)
- Small volumes (knee joint: ̴0.5 ml )
- Rapid turnover ( ̴2 hours)
What are the funcitons of synoival fluid?
- Nutrition of cartilage (articular c., menisci/discs)
- Removal of waste products
- Lubrication so less friction so less wear
How is the thin film of glycoproteins such as lubricin formed on the articular surface?
Glycoproteins bind to receptors on the articular surfaces to form a thin film
How are joint surfaces kept separated?
Kept apart by liquid pressure
When does viscosity of synovial fluid change?
–Viscosity changes with load and velocity of movement
How is fluid volume increased in the joint cavity?
–Fluid that is present in the cartilage is squeezed out into the synovial cavity to increase fluid volume
What are bursae?
Fluid filled sacs that counter friction in a joint
They are line by synovial membrane and are filled with viscous synovial fluid
Inflammation results in bursitis
How does the ageing process affect the joint?
•Viscosity of synovial fluid increases
–Slower joint movements
–Reduced lubrication
•Water content of cartilage decreases
–Reduced shock absorption
→Less protection of articular surfaces & increased risk of damage
Osteoarthritis
