Joints, synovial fluid and cartilage Flashcards
What are the 3 structural types of joints?
Fibrous
Cartilaginous
Synovial
Describe what fibrous joints are
Union of two bones where they are connected by dense fibrous connective tissue - essentially just collagen
This makes them very strong, and not very movey
Where are fibrous joints found?
Cranial sutures
Periodontal ligament
Interosseus membranes
What are cartilaginous joints?
Joints in which the bones are linked by cartilage
2 types:
Synchondrosis / primary cartilaginous
Symphysis / secondary cartilaginous
What is the difference between synchondrosis and symphysis?
Synchondrosis (primary):
- only hyaline cartilage
Symphysis (secondary):
- hyaline cartilage & fibrocartilage
Give an example of where a synchondrosis joint is found
Synchondrosis (primary)
Growth plate of growing long bones
Give an example of where you would find a symphysis joint
symphysis (secondary cartilaginous)
Intervertebral discs
Identify the main features of a synovial joint
Aside from the common features in the diagram before - what else may synovial joints contain?
Articular discs - eg meniscus of knee
Ligaments - can be within or outside capsule
Bursae
What are bursae?
Little fluid filled pillow things that are found round joints
Act as cushion things
What are the types of synovial joint?
Plane
Hinge
Pivot
Condylar (ellipsoid)
Saddle
Ball & socket
identify the types of joint shown in each example
What determines the stability of joints?
1) The shape of articulating surfaces
* Shallow means more mobile joint but less stable
2) Ligaments and capsules surrounding the joint
3) Muscles surrounding the joint
What type of cartilage is ‘articular cartilage’?
Hyaline cartilage
If viewed histologically - what layers are present in articular cartilage?
Superficial / tangential layer
Transitional layer
What are the main features of the superficial (tangential) layer of articular cartilage?
Layer closest to the articular surface
Identifiable by the presence of Lots of flat chondrocytes
These chondrocytes produce collagen and glycoproteins (eg lubricin)
What are the main features of the transitional layer of articular cartilage?
Fewer and more rounded looking chondrocytes
These produce proteoglycans such as aggrecan
How does the orientation of chondrocytes change as you move from superficial to deep?
What is hyaline cartilage predominantly made up of?
Why is this suited for its structure?
>75% water
Water is incompressible
Whats the difference between proteoglycans, glycoproteins and Glycosaminoglycans (GAGs)?
Glycoproteins - proteins to which oligosaccharide chains are attached
Proteoglycans - proteins that are heavily glycosylated (= a protein core to which one or more GAGs attach), i.e. tend to be more carb than protein
Glycosaminoglycans or GAGs (e.g. hyaluronic acid): long unbranched polysaccharides, which are highly polar and thus attract water
How thick is articular cartilage
average: 2-3 mm
(interphalangeal joint: 1 mm)
(patella: 5-6 mm)
Cartilage has 3 overall distinct features which separate it from other types of tissue
What are these?
Cartilage is:
- avascular
- aneural
- alymphatic
In reality - at the peripheries of cartilage - you find things like blood vessels etc but in general this is true so shut up
If cartilage is avascular and alymphatic - then how does it transport nutrients and waste to/from its cells?
Through synovial fluid
What produces synovial fluid?
Synoviocytes in the synovium (synovial membrane)
Describe the main features of the synovium?
Synovium = synovial membrane
Contains synoviocytes
Has a rich capillary network
Has no epithelial lining
How is the transport of nutrients between blood and the synovium done?
Direct exchange of oxygen, carbon dioxide & metabolites between blood & synovial fluid
What are the different types of synoviocytes?
Type A & B
Type A - Remove debris and contribute to SF production
Type B - Main producer of SF
What is synovial fluid?
What is it made of?
Viscous fluid
Made up of Hyaluronic acid & lubricin
Also has fluid component from plasma
Rapid turnover (around 2 hours)
What type of cells do type A & B synoviocytes resemble?
Type A synoviocytes - resemble Macrophages
Type B synoviocytes - resemble fibroblasts
What are the functions of synovial fluid?
Nutrition of cartilage
Removal of waste products
Lubing everything up xx
What are the 3 types of lubrication?
Boundary lubrication
Hydrodynamic lubrication
Weeping lubrication
What is boundary lubrication?
Glycoproteins such as lubricin bind to receptors on articular surfaces to form a thin film
What is hydrodynamic lubrication?
Think of aquaplaning
Surfaces kept apart by liquid pressure
Viscosity changes with load and velocity of movement
What is weeping lubrication?
Fluid that is present in the cartilage is squeezed out into the synovial cavity to increase fluid volume
What is the inflammation of bursae called?
Bursitis funnily enough
How does ageing affect joints?
2 main things that change…
1) Increased viscosity of synovial fluid
* Slower movements, less lubrication
2) Decreased water content of articular cartilage
* Reduced shock absorption
Both these changes mean there is less protection to older joints
