201 L6 Flashcards
Tissues under load
Name the Types of mechanical loads.
Tension Compression Shear Torsion Bending
What mechanical loads affect cartilage?
Mainly compression
Also shear
What mechanical loads affect bone?
Tension and compression in equal amounts
What mechanical loads does articular cartilage experience?
Main = Compression Less = Tension and shear at surface
What form of cartilage is articular cartilage?
Hyaline cartilage
Where is articular cartilage found?
On the ends of bones between joints.
What is the function of articular cartilage?
Limits the amount of shear stress and friction
Provides a coating for the underlying bone
What is the function of cartilage with respect to load bearing?
Cartilage spreads the load
What happens to cartilage when it meets the blood supply?
It dies
Name the zones in articular cartilage?
Articular surface Superficial zone Middle zone Deep zone Calcified zone Subchondral bone Bone
In the ———- zone the ——– fibres are ——– to the ——– surface providing a smooth surface to minimise —— stress.
In the superficial zone the collagen fibres are parallel to the articular surface providing a smooth surface
to minimise shear stress.
In the ———- zone the ——– fibres go in — ——–. This makes this zone the ——— load bearing zone.
In the middle zone the collagen fibres go in 3 dimensions. This makes the zone the most load bearing zone.
In the ——– zone the ———– fibres are ———— to the surface. Here the fibres cross the ——- into the ——- zone and plug into the ——–.
In the deep zone the collagen fibres are perpendicular to the surface. Here the fibres cross the tidemark into the calcified zone and plug into the bone.
Loading cycle of articular cartilage:
- In recently ———— cartilage ——— charges on the repeating ——— units attract ——— ions into the ———- from the ——– space. This ————- the —— concentration in the ——–.
- The —— in ionic concentration creates an —— gradient which draws ——- into the ——-. The cartilage begins to ——– with the influx of ———.
- As the cartilage swells the ——– is placed under increasing ——. Eventually the ———- force = the ——— force, and the cartilage stops swelling. This is known as the ——— ———–.
- When a —— is introduced the ——– ions and ——– are squeezed ——- of the cartilage and back into the —– space and ——— fluid.
- The loss of ——- reduces the ——— of the cartilage, which is called ——–. This pushes the ——– charges closer together. Eventually the ———— load will be supported by the —— component and the repulsive ——– charges. The cartilage will stop ——— when it is ——– equilibrium
- In recently unloaded cartilage negative charges on the repeating dissacharide units attract + ions into the cartilage from the joint space. This increases the ionic concentration in the matrix.
- The increase in ionic concentration creates an osmotic gradient which draws water into the matrix. The cartilage begins to swell with the influx of water.
- As the cartilage swells the collagen is placed under increasing tension. Eventually the swelling force = the tension force, and the cartilage stops swelling. This is known as the unloaded equilibrium.
- When a load is introduced the + ions and water are squeezed out of the cartilage and back into the joint space and synovial fluid.
- The loss of water reduces the volume of the cartilage, which is called creep. This pushes the negative charges closer together. Eventually the compressive load will be supported by the solid component and the repulsive negative charges. The cartilage will stop swelling when it is loaded equilibrium.
What collagen fibres are in articular cartilage?
Type 2
If the articular cartilage loses its ability of —– and the strength of the —— network it will start of wear away.
If the articular cartilage loses its ability of hydration and the strength of the collagen network it will start of wear away.
The quicker you —- the cartilage the quicker the —– comes out.
This refers to ———-
The quicker you load the cartilage the quicker the water comes out.
This refers to viscoelastic
When the load is first introduced to the articular cartilage what component supports the load first and why?
Fluid component can’t escape immediately takes a bit of time so when the load is first introduced the fluid component is what actually supports the load first
What tissues does Osteoarthritis affect?
All the tissues of the joints: Cartilage Bone Muscle Ligaments
What body parts are commonly affected by osteoarthritis?
Knee, hands and hips
Osteoarthritis typically occurs ——- in life, usually after age ——, although may start ——– in the case of joint ——-.
Osteoarthritis typically occurs later in life, usually after age 50, although may start earlier in the case of joint injury.
Other than joint replacement surgery there is no cure
What is the causation of primary and secondary osteoarthritis?
Primary = unknown secondary = injury
What are some risk factors of osteoarthritis?
Age
obesity
genetics
What happens to ECM and chondrocytes in osteoarthritis?
Fibrillation of collagen network at zone 1
Breakdown of collagen network, swelling of tissue due to increased water presence
Loss of proteoglycans results in fissure cracks
Cells divide forming clusters of cells, there is futile repair and secretion of matrix
The zones wear away resulting in osteophytes - bony knobs at joint margins.
