Edexcel AS Biology- blood clottingWatch
Platelets come into contact with an area of an artery wall which has become damaged, changing their shape from flattened disks to long thin projections. The platelets stick together, forming a temporary plug. Thromboplastin, released from damaged tissue and platelets, as well as Ca2+ and vitamin K from the plasma, are released which changes the soluble prothrombin into thrombin. As this is an enzyme, it catalyses soluble fibrinogen to change into the insoluble fibrin. The fibrin strands form a tangled mesh which trap a bundle of blood cells, forming a clot.'
Does the order of this sound suitable? Also at what part of the atherosclerosis process would this fit in- I'm assuming at the second stage where the white blood cells go to the damaged artery wall?
a) Vitamin K is NOT involved directly in blood clotting - it is necessary for the synthesis of certain clotting factors (factors II, V, VII and X [deficiency of factor X causes Christmas disease, a bleeding didorder] if you are aiming for A*) in the liver.
b) There is no direct connection between clotting and atherosclerosis - having said this, atherosclerosis (deposition of lipoid material in the intima of the arteriolar wall causes narrowing (stenosis) and hence reduced blood supply to the part supplied by that artery - this means slowing of blood flow) leads to a greater probability of a clot (thrombus) forming e.g. in the coronary artery(ies) in heart attack (myocardial infarction).