Hematopoiesis occurs primarily in the bone marrow, where pluripotent hematopoietic stem cells differentiate into all blood cell lineages through growth factor-mediated signaling — erythropoietin (EPO) from the kidneys drives red blood cell production, thrombopoietin (TPO) regulates platelet production, and colony-stimulating factors (G-CSF, GM-CSF) stimulate white blood cell development. The coagulation cascade involves intrinsic and extrinsic pathways converging at factor X activation, ultimately converting prothrombin to thrombin, which cleaves fibrinogen into fibrin monomers that polymerize to form a stable clot. Hemostatic balance is maintained by anticoagulant mechanisms (antithrombin III, protein C, protein S) and fibrinolysis (plasminogen to plasmin conversion) — imbalance causes either hemorrhagic or thrombotic disorders.