Flashcards in Joint Physiology Deck (35):
What is a fibrous joint?
Bones united by a fibrous tissue
What is a cartilaginous joint?
bones united by cartilage
What is the synovial membrane?
vascular connective tissue with capillary networks and lymphatics that lines the inner aspect of fibrous capsule
contains synovial cells (fibroblasts) which produces the synovial fluid
What covers the articular surfaces of bones?
How do you differentiate between a simple and compound synovial joint?
simple - one pair of articular surfaces
Compound - more than one pair of articular surfaces
What is the physiological functions of joints?
What are the 3 main roles of joints during purposeful motion?
- stress distribution
- confer stability
- joint lubrication
What is joint lubrication provided by?
- cartilage interstitial fluid
- Synovium - derived hyaluronic acid (mucin) - a polymer of disaccharides
- Synovium-derived lubrcin - a glycoprotein
What helps to confer stability?
shape of articular component
What are the functions of synovial fluid?
- lubricates joints
- facilitates joint movements to reduce friction
- helps minimise wear and tear
- aids in nutrition of articular cartilage (avascular)
- supplies chondrocytes with O2 and nutrients and remove CO2 and waste products
Give the general characteristics of synovial fluid?
- fills the joint cavity
- continuously replenished
- high viscosity (varies with joint movement)
- other constituents are derived from blood plasma
- contain few cells (mainly mononuclear leucocytes)
How does the synovial fluid change during movement in terms of viscosity and elasticity?
Rapid movement is associated with decreased viscosity and increased elasticity
What does normal synovial fluid look like?
clear and colourless
What happens to the synovial fluid in pathology?
WBC count increased in inflam and sepsis
Turns red in traumatic synovial tap and in haemorrhage arthritis
What are the main functions of articular cartilage and why?
low friction lubricated gliding surface to help prevent wear and tear
distributes contact pressure to subchondral bone
Name the layers of articular cartilage from the articular surface down.
In the different zone of articular cartilage, how do the collagen fibres differ?
organization of collagen fibres
relative content of cartilage component
What is the articular cartilage made of? Describe it’s properties.
elastic and has sponge like properties
What is the ECM of the articular cartilage made up of?
water 70% (most at top zone)
collagen type 2 20%
proteoglycans 10% (highest conc in middle and deep zone)
What happens to the cartilage water, chondroitin and collagen content with age?
What is the purpose of water in the articular cartilage component, water?
Maintain the resiliency of the tissue and contribute to the nutrition and lubrication system
What is the function of collagen in the articular cartilage?
Maintain cartilage architecture
Provides tensile stiffness and strength
What is the proteoglycan component made up of?
mainly of glycosaminoglycan e.g. chondroitin sulphate
Give the function of having proteoglycans in the cartilage.
Responsible for the compressive properties associated with load bearing
What synthesises, organises, degrades and maintains the ECM of articular cartilage?
The articular cartilage is avascular. How does it receive nutrients etc?
Chondrocytes receive nutrients and O2 via the synovial membrane
The rate of degradation is/is not equal to the rate at which it is replaced?
Is - in normal jointa
What could change the mechanical properties of cartilage?
changes in the relative amount of water, collagen and proteoglycans
If the rate of ECM degradation exceeded the rate of it's synthesis, what would happen?
What are the catabolic factors relating to cartilage matrix turnover?
Stimulate proteolytic enzymes and inhibit proteoglycan synthesis
What are the anabolic factors relating to cartilage matrix turnover?
Stimulate proteoglycan synthesis and counteract effects of IL-1
Name the markers of cartilage breakdown?
Increased levels of serum and synovial keratin sulphate
Increased levels of type 2 collagen in synovial fluid
What may go wrong in a joint?
- cartilage and synovial composition and function deteriorate leading to wear and tear
- synovial cell proliferation and inflammation
-deposition of salt crystals
- injury and inflammation to periarticular structures
What are the effects on the subchondral bone of cartilage deterioration?
- Cyst formation
- Sclerosis (increased density)
- Osetophyte formation (spiky bony formation into joint cavity)