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Anatomy & Physiology: Blood and Hemostasis

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  • What are the primary functions of blood?
    Transportation of gases, nutrients, hormones, and wastes; regulation of pH and ion composition; restriction of fluid loss at injury sites; defense against toxins and pathogens; stabilization of body temperature.
  • What are the main components of blood?
    Blood consists of plasma (fluid matrix) and formed elements (RBCs, WBCs, and platelets).
  • What is plasma and what are its major proteins?
    Plasma is ~92% water and contains proteins: albumins (osmotic pressure, transport), globulins (antibodies, transport), and fibrinogen (clotting).
  • Describe the structure and function of red blood cells (RBCs).
    RBCs are biconcave discs without nuclei, maximizing surface area for gas exchange and flexibility to pass through capillaries; they carry oxygen via hemoglobin.
  • What is hemoglobin and its role in RBCs?
    Hemoglobin is a protein with four chains (2 alpha, 2 beta) each with a heme group containing iron; it binds oxygen to form oxyhemoglobin for transport.
  • How are RBCs broken down and recycled?
    Macrophages digest RBCs; heme is converted to biliverdin then bilirubin, excreted in bile; iron is recycled via transferrin for new RBC production.
  • What is erythropoiesis and where does it occur?
    Erythropoiesis is RBC production occurring in red bone marrow, regulated by erythropoietin (EPO) released from kidneys in response to hypoxia.
  • What factors regulate erythropoiesis?
    Adequate amino acids, iron, vitamins B12, B6, folic acid, and erythropoietin (EPO) are essential for normal RBC production.
  • What determines ABO and Rh blood types?
    Blood types are determined by antigens (agglutinogens) on RBC membranes: A, B, both (AB), or none (O), plus Rh factor (positive or negative).
  • What causes hemolytic disease of the newborn (HDN)?
    HDN occurs when an Rh-negative mother produces antibodies against Rh-positive fetal RBCs, leading to fetal RBC destruction in subsequent pregnancies.
  • What are the main functions of white blood cells (WBCs)?
    WBCs defend against pathogens, remove toxins and wastes, and can migrate into tissues to perform immune functions.
  • Name the types of WBCs and their general roles.
    Neutrophils, eosinophils, basophils, monocytes (nonspecific defense); lymphocytes (specific immunity producing antibodies).
  • What is the role of neutrophils in immune defense?
    Neutrophils are first responders that phagocytize bacteria and release enzymes and chemicals to promote inflammation and attract other immune cells.
  • How do eosinophils contribute to immune response?
    Eosinophils attack antibody-marked pathogens, release toxic compounds, and increase during allergic reactions.
  • What substances do basophils release and their effects?
    Basophils release histamine (vasodilation) and heparin (prevents clotting), enhancing inflammation.
  • Describe the origin and differentiation of WBCs.
    WBCs arise from hemocytoblasts; myeloid stem cells produce granulocytes and monocytes; lymphoid stem cells produce lymphocytes.
  • What are platelets and their main functions?
    Platelets are cell fragments that release clotting chemicals, form platelet plugs, and contract to shrink clots.
  • What is hemostasis and its three phases?
    Hemostasis stops bleeding via: 1) vascular phase (vasospasm), 2) platelet phase (plug formation), 3) coagulation phase (fibrin clot formation).
  • What triggers the vascular phase of hemostasis?
    Endothelial injury causes smooth muscle contraction, endothelial cell contraction exposing basal lamina, and release of endothelins.
  • Explain the coagulation pathways leading to clot formation.
    Extrinsic and intrinsic pathways activate Factor X, leading to prothrombinase formation, thrombin activation, and conversion of fibrinogen to fibrin.