1. When healthy lung tissue has been replaced with nonfunctional cancerous tissue, the blood is unable to pick up an adequate amount of oxygen from the lungs regardless of the RBC count.

2. Erythropoiesis is stimulated by erythropoietin, which is secreted by the kidneys. As nephrons degenerate, erythropoietin secretion declines and the hematocrit and RBC count drop.

3. She exhibits multiple risk factors for anemia: her age; a probability of poor nutrition suggested by her poverty and apparent alcoholism; inhibition of folic acid metabolism by the alcohol; and possible hemorrhage due to the accident.

4. Loosely speaking, the blood cells "clump" in both processes, but the mechanisms are entirely different. In coagulation, they become stuck to the threads of fibrin a little like insects in a spider web. In agglutination, RBCs are stuck together by antibody molecules.

5. Prothrombin is an enzyme. Like all enzymes, it is not consumed by the reaction, so it is used repeatedly and a very small amount is needed to produce a large quantity of reaction product. Fibrinogen, however, is the substrate consumed by the reaction to make fibrin; therefore, larger quantities of it are needed for clotting.

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