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Anatomy & Physiology: Blood and Hemostasis

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Termini in questo insieme (27)

  • Functions of Blood
    Transport of O2, nutrients, wastes, hormones; Regulation of temperature, pH, fluid volume; Protection against blood loss and infection.
  • Composition of Blood
    Blood is connective tissue with plasma (nonliving fluid matrix) and formed elements (RBCs, WBCs, platelets).
  • Hematocrit
    Percentage of blood volume occupied by RBCs; normal ~45% (males 47% ± 5%, females 42% ± 5%).
  • Physical Characteristics of Blood
    Sticky, opaque fluid with metallic taste; color varies with O2 content; pH 7.35–7.45; ~8% body weight; volume 5–6 L males, 4–5 L females.
  • Plasma Composition
    About 90% water with dissolved solutes including nutrients, gases, hormones, wastes, and plasma proteins like albumin (60%).
  • Formed Elements
    Include erythrocytes (RBCs), leukocytes (WBCs), and platelets; only WBCs are complete cells.
  • Erythrocyte Structure
    Small (7.5 μm), biconcave, anucleate cells filled with hemoglobin; flexible due to spectrin protein.
  • Hemoglobin Structure
    Protein with four polypeptide chains (2 alpha, 2 beta) each bound to a heme group containing iron that binds O2.
  • Erythrocyte Function
    Transport respiratory gases; each Hb molecule carries 4 O2; RBC contains ~250 million Hb molecules.
  • Erythropoiesis
    Process of RBC formation in red bone marrow; takes ~15 days; regulated by erythropoietin (EPO).
  • Erythropoietin (EPO)
    Hormone from kidneys that stimulates RBC production in response to hypoxia (low O2).
  • Dietary Requirements for Erythropoiesis
    Amino acids, iron (stored as ferritin/hemosiderin, transported by transferrin), vitamin B12, and folic acid.
  • RBC Life Span and Destruction
    Live 100–120 days; old RBCs broken down by macrophages; heme degraded to bilirubin, iron recycled.
  • Anemia
    Condition with low O2-carrying capacity; causes include blood loss, low RBC production, or high RBC destruction.
  • Polycythemia
    Excess RBCs increasing blood viscosity; caused by bone marrow cancer or hypoxia-induced EPO increase.
  • Leukocytes (WBCs)
    Complete cells with nuclei; defend against disease; classified as granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).
  • Neutrophils
    Most abundant WBCs (50–70%); multilobed nucleus; phagocytic bacteria slayers; kill microbes via respiratory burst.
  • Eosinophils
    2–4% of WBCs; bilobed nucleus; red granules; attack parasitic worms; involved in allergies and asthma.
  • Basophils
    Rarest WBCs (0.5–1%); bilobed nucleus; granules contain histamine which promotes inflammation and attracts WBCs.
  • Lymphocytes
    25–45% of WBCs; large nucleus; key in immunity; T cells attack infected cells, B cells produce antibodies.
  • Monocytes
    Largest WBCs (3–8%); kidney-shaped nucleus; differentiate into macrophages; phagocytic and activate lymphocytes.
  • Platelets
    Cell fragments from megakaryocytes; contain clotting chemicals; form temporary platelet plugs in vessel injury.
  • Hemostasis Steps
    1) Vascular spasm (vasoconstriction), 2) Platelet plug formation, 3) Coagulation (fibrin clot formation).
  • Coagulation Pathways
    Intrinsic (clotting factors in blood) and extrinsic (tissue factor outside blood) pathways converge to activate factor X and form prothrombin activator.
  • Thrombin Role
    Converts prothrombin to thrombin, which converts fibrinogen to fibrin forming the clot mesh.
  • Clot Retraction and Fibrinolysis
    Platelets contract to shrink clot; plasmin enzyme dissolves clot after repair.
  • Blood Transfusions and Typing
    Blood groups based on A, B, and Rh antigens; mismatched transfusions cause agglutination and hemolysis.