Red Blood Cell
Red blood cells are the cells in the blood stream that bring oxygen from the lungs to the tissues and then carbon dioxide from the tissues to the lungs to be breathed out.
Platelets are actually fragments of cells that are important in blood clotting. At a site of vascular damage, they are activated by von Willebrand factor and collagen which promotes their binding together with fibrinogen and forming fibrin nets to prevent the loss of blood. They can also further activate other platelets in the area by releasing thromboxane (TXA2)
If the formation of a fibrin net does not completely close a wound, the body forms a blood clot. This is activated by the clotting cascade which is broken into the intrinsic, extrinsic, and common pathway. It include one factor activating another, which activates another, etc until a fibrin clot with platelets and red blood cells is formed to block the wound.
Sickle Cell Anemia
In sickle cell anemia, red blood cells loose their donut-like shape and morph into sickle-shaped cells. This is due to a mutation in both beta hemoglobin genes (HBB). These cells can get stuck in capillaries which can be extremely painful.
Von Willebrand Disease
Von Willebrand disease occurs with a loss of von Willebrand factor which plays an important role in activating platelets at sites of damage. This leads to bleeding problems which is variable depending on the extent of VWF loss.
Hemophilia is a genetic disorder that leads to the inability to form clots by the intrinsic clotting pathway. Loss of factor 9 occurs in hemophilia B and loss of factor 8 occurs in hemophilia A. Patients with hemophilia have increased bleeding which can be deadly.
Sickle Cell Anemia -> Red blood cell
Hydroxyurea promotes the expression of fetal hemoglobin, which can replace the mutated beta hemoglobin (HBB*). It also decreases white blood cell levels and thus decreases inflammation.
Von Willebrand Disease -> Platelet
Desmopressin promotes the release of von Willebrand factor from endothelial cells which helps to increase the decreased levels of VWF in this disease. It is not effective in patients that have a complete absence of VWF.
Hemophilia -> Blood Clot
As hemophilia patients have either a defect in factor 9 (hemophilia B) or factor 8 (hemophilia A), acute bleeding can be treated by replacing lost clotting factors with clotting factor concentrate.