Musculoskeletal 4 Flashcards
What is a disaccharide?
Two sugars
What is a repeating disaccharide unit called?
A glycosaminoglycans
Examples of a glycosaminoglycan?
Chondroitin (CS) and keratin sulphate (KS)
What is a proteoglycan?
Many glycosaminoglycans attached to a protein core
Example of a proteoglycan?
Aggrecan
Why do GAGs stand out like bristles on s brush on a proteoglycan?
Because the negative charges repel each other
What do proteoglycan attach to?
A long hyaluronic acid chain
What is a hyaluronic acid chain?
A large proteoglycan complex
What can extremely large hyaluronic acid chain molecules attach to?
Collagen fibre
What is recently unloaded cartilage like?
Has just had a compressive force taken away
What is the first stage of the loading cycle of articular cartilage?
Negative charges on the repeating disaccharide units cataract positive ions into the cartilage from the joint space; which increases ion concentration in the matrix
What mobile fluids enter the articular cartilage during the loading phase?
Ca k Na H2O Nutrients O2
How many glycosaminoglycans are attached to a core protein?
125 CS
50 KS
What’s the second phase of the articular cartilage loading cycle?
The increase in ion concentration creates an osmotic pressure/gradient which draws water into the matrix; the cartilage begins to swell with the influx of water
What is the third step of the loading cycle of articular cartilage?
As the cartilage swells the collagen is placed under increasing tension. Eventually the swelling force= the tensional forces, and the cartilage stops swelling. This is known as the unloaded equilibrium
What is the fourth step of the articular cartilage loading cycle?
When a load is introduced the fluid phase (water and positive ions- ie Ca, K, Na etc) is squeezes out of the cartilage and back into joint space and synovial fluid
What’s the last phase of the loading cycle of articular cartilage?
The loss of the fluid phase reduces the volume of cartilage (creep). This pushed the negative charges closer together. Eventually the compressive load will be supported by the solid phase and the repulsion of the negative charges. The cartilage will stop shrinking = loaded equilibrium
What are all synovial joints surrounded and enclosed by?
A joint capsule
What does the joint capsule form?
A “sleeve” around the joint connecting the ends of the contributing bones