Joints and Synovial Fluid Flashcards
What are the three main types of joint?
Fibrous
Cartilaginous
Synovial
Describe the mobility of the three main types of joint?
Fibrous- very immobile
Cartilaginous- slightly mobile but still not very mobile
Synovial- mobile
What makes up the joints in fibrous joints?
Fibrous joints- collagen fibres and fibrous connective tissue
What makes up the joints in cartilaginous joints?
Cartilage and some collagen fibres
Where in the body are fibrous joints found?
Periodontal ligament
Cranial sutures
Interosseus membranes
What are the two types of cartilaginous joints?
Primary cartilaginous or synchondrosis
Secondary cartilaginous or symphysis
What makes up primary and secondary cartilaginous joints?
Primary- Hyaline cartilage only
Secondary- Hyaline cartilage and fibrocartilage
Where are primary and secondary cartilaginous joints found?
Primary- growth plate
Secondary- intervertebral discs
What are the common and rarer features of a synovial joint?
Common features: -Synovial cavity (fluid filled) -Articular cartilage -Fibrous capsule -Synovial membrane Rarer features: -Articular discs -Bursa -Ligaments
What are the different kinds of synovial joints?
Plane Hinge Pivot Condylar Ellipsoid Ball and socket
What are the factors contributing to joint stability?
Shape of articulating surfaces
Capsules and ligaments
Muscles
What are the histological differences between hyaline cartilage and fibrocartilage?
Fibres are present in hyaline cartilage but not as densely packed as in fibrocartilage so the hyaline fibres do not show on histology.
What are the characteristics of the superficial/tangential layer of articular cartilage?
Flattened chondrocytes that produce collagen and glycoproteins
What are the characteristics of the transitional layer of articular cartilage?
Round chondrocytes that produce proteoglycans such as aggrecan
Describe the orientation of collagen fibres in articular cartilage?
They lie parallel to the surface in the superficial layer, become more oblique in the transitional layer and lie perpendicular to the surface in the deep layers
What is the water content of articular cartilage and how does it change with age?
~75%, decreasing with age
What are glycoproteins?
Proteins to which oligosaccharide chains are attached
What are proteoglycans?
Proteins that are heavily glycosylated
What are glycosaminoglycans?
Long, unbranched polysaccharides that are highly polar and attract water
What influences the thickness of articular cartilage?
Forces acting on the cartilage
How do nutrients reach the cartilage within joints and why is this necessary?
Nutrients reach the joint through the synovial fluid. This is necessary because the cartilage is avascular, alymphatic and aneural, except from at the peripheries where there are some vessels
Describe the characteristics of the synovium
Synoviocytes producing the fluid
Rich capillary network, through which exchange of nutrients between blood and synovial fluid
No epithelial lining so synovial fluid can enter joint easily
What are the characteristics of the two types of synoviocytes?
Type A- look like macrophages, removes debris, contributes to synovial fluid production
Type B- fibroblast like, main producer of synovial fluid
What are the contents of synovial fluid?
Viscous fluid
Hyaluronic acid
Lubricin
Fluid component (taken from blood plasma)
What are the functions of synovial fluid?
Nutrition of cartilage
Removal of waste products
Lubrication to reduce wear
What are the different kinds of lubrication?
Boundary- glycoproteins bind to receptors on articular surface to form a thin film
Hydrodynamic- surfaces kept apart by liquid pressure
Weeping- fluid that is present in the cartilage is squeezed out into the synovial cavity to increase fluid volume
What are the characteristics of bursae?
Synovial membrane
Fluid-filled
Reduces friction
What affects do ageing have on joints?
Viscosity of synovial fluid increases- slower joint movements and reduced lubrication
Water content of cartilage decreases- reduced shock absorption
Both cause less protection of articular surfaces and an increased risk of damage
