Physiology of joints Flashcards
What are the 3 main types of joint?
- Synovial (Diarthrosis)
- Fibrous (Synarthrosis)
- Cartilaginous (Amphiarthrosis)
What are fibrous joints?
Fibrous joints are joints in which bones are united by fibrous tissue
They do not allow much or any movement
What are the 2 two types of fibrous joint?
- Sutures
- Syndesmoses
What are cartilaginous joints?
These are joints in which bones are united by cartilage, allowing limited movement
What are synovial joints?
Synovial joints are joints in which bones are seperated by a synovial cavity, filled with synovial fluid, and are united by a fibrous capsule, along with other soft tissue structures (e.g. tendons, ligaments)
What lines the inner surface of a synovial joint capsule?
The inner aspect of the fibrous capsule is lined with a synovial membrane containing synovial cells (Fibroblasts), which produce and absorb synovial fluid
What makes up the outer surface of a synovial joint capsule?
Hyaline cartilage
What is meant by a simple synovial joint?
One in which there are only 2 articular surfaces (E.g. MCP)
What is meant by a compound synovial joint?
One in which there is more than 2 articular surfaces (E.g. knee joint)
What are some of the functions of a joint?
During purposeful motion, joints provide stress distribution, confer stability and provide joint lubrication
How do joints confer stability?
They confer stability via forming the shape of the articular component, providing ligaments for stability and forming synovial fluid, which acts as an adhesive seal that freely permits sliding motion between surfaces
What are the main 2 lubricants found in synovial fluid?
- Synovium-derived hyaluronic acid (Mucin)
- Synovium-derived lubricin
How does synovial fluid change during movement?
During movement, synovial fluid can change in viscosity and elasticity
Rapid movement is associated with decreased viscosity and increased elasticity
What can cause red synovial fluid?
Haemorrhage arthritis
Traumatic synovial tap
What will cause straw coloured or yellow synovial fluid with a low viscosity?
Inflammatory conditions
What will cause opaque synovial fluid?
Septic conditions
What is the function of articular cartilage?
The articular (hyaline) cartilage of the synovial joint provides a low friction, lubricated gliding surface, helping to prevent wear and tear
What are the 4 main zones of articular cartilage?
- Superficial zone
- Middle zone
- Deep zone
- Calcified bone
What is the composition of the ECM of articular cartilage?
Water (70%)
Mainly type II collagen (20%)
Proteoglycans (10%)
Where is most of the water in the articular cartilage found?
Superficial zone (80%)
How does the composition of articular cartilage change with age?
Water content and cartilage content decrease with age, decreasing stability of architecture and decreasing tensile strength
How is the ECM of articular cartilage broken down?
The ECM of the cartilage is broken down mostly by the stimulation of proteolytic enzymes and inhibition of proteoglycan synthesis
This is performed by tumour necrosis factor a (TNFa) and interleukin-1 (IL-1)
How is ECM built up in articular cartilage?
The ECM is built up by the stimulation of proteoglycan synthesis and counteraction of the effects of IL-1
This is performed by tumour growth factor ß (TGFß) and insulin-like growth factor 1 (IGF-1)
