Joints and Synovial fluid Flashcards
What are the three classes of joints?
Fibrous
Cartilaginous
Synovial
Describe a fibrous joint
Bone-fibrocartilage-Bone: e.g. cranial sutures
Describe a cartilaginous joint
Bone- cartilage-Bone. Two types
Primary, only hyaline cartilage- synchondrosis
Secondary, fibocartlage and hyaline- symphysisi
Describe a synovial joint
More complicated. Occur at two bones that articulate to produce movement. The bones are lined by articular cartilage and a synovial membrane. Synovial fluid is produced by these membranes adn the whole structure is surrounded by a fibrous cartilage
may also contain articular discs, ligaments and bursae
What are some examples of synovial joints
Plane- permits small amount of gliding movement e.g. between transverse process’
Condylar (ellipsoid)- flexion, extension, abduct, adduct, not able to rotate 360. e.g. radiocarpal
Hinge- able to flex and extend e.g. elbow
Saddle- flex, extend, abduct, adduct. e.g. thumb
Pivot: allows rotational movement on a single axis: axial atlas joint
Ball and socket: allows flexion, rotation, abduction, adduction and circumduction
What increases joints stability
shape of articualting surfaces
capsule and ligaments that surround them
muscles that support them
What is the role of cartilage
To prevent damage to joints. synovial joints can contain two types of cartilage. Hyaline(articualr) cartilage provides lubrication while fibrocartilage provides support
Describe the structure of hyaline cartilage
Avascular structure typically 2-3cm thick that contains 75% water and different cells called chondrocytes.
superifical layer contain flattened chondrocytes that produce collagen adn glycoproteins e.g. lubricin
Transtional layer contains round chondrocytes that produce proteoglycans such as aggrecan
What is the synovial membrane?
Lines the cartilage and synoviocytes producing the synovial fluid. There is a rich capillary network with no epithelial lining. There is a direct exchange of oxygen, carbon dioxide and metabolites between blood and synovial fluid. There are two types of synoviocytes:
Type A- look likemacrophages, remove debris, contribute to synovial fluid production
Tybe B- fibroblast like, main producer of synovial fluid
What is synovial fluid?
Viscous fluid that consists of hyaluronic acid and lubricin. There is also a fluid component derived from blood plasma It occurs in small volumes (0.5ml) and has a rapid turnover every two hours.
What is the role of synovial fluid
Provides lubrication for the joints, allowing for less wear.
Also provides nutrition to articular cartilage and menisci
Removes waste from from articular cartilage and menisci
How does the synovial fluid produce lubrication?
Works by creating a boundary. Glycoproteins such a lubricin bind to receptors on articulation surfaces to form a thin film. They are hydrodynamic and the surfaces are kept apart by liquid pressure. Viscocity changes with loadd and velocity of movement. Weeping also allows the fluid in articular cartilage to be squeezed out
What are the bursae?
Physcial barriers that stop tendons and muscles rubbing on the bone. They contain synovial membrane and are fluid filled to reduce friction
What happens to these processes when you age?
The viscosity of synovial fluid icnreases, reducing joint movement. Water content of cartilage decreases, reducing shock absorption. This leads to an increased risk of damage
