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Anatomy & Physiology: Blood - Structure, Function, and Disorders

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Termini in questo insieme (29)

  • Functions of Blood

    Transport: delivers O2, nutrients, wastes, hormones.
    Regulation: maintains temperature, pH, fluid volume.
    Protection: prevents 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 4-6 L.

  • Blood Plasma Composition

    About 90% water with dissolved solutes including nutrients, gases, hormones, wastes, and plasma proteins like albumin, globulins, and fibrinogen.

  • Erythrocyte Structure

    Biconcave, anucleate cells filled with hemoglobin; flexible due to spectrin protein; diameter ~7.5 μm.

  • Hemoglobin Structure

    Protein with 4 polypeptide chains (2 alpha, 2 beta), each bound to a heme group with iron that binds O2.

  • Erythrocyte Function

    Transport respiratory gases: O2 binds to heme forming oxyhemoglobin; CO2 binds to globin forming carbaminohemoglobin.

  • Erythropoiesis

    Formation of RBCs in red bone marrow from hematopoietic stem cells, regulated by erythropoietin (EPO).

  • Erythropoietin (EPO) Regulation

    Released by kidneys in response to hypoxia; stimulates RBC production; inhibited by high O2 or RBC count.

  • Dietary Requirements for RBC Production

    Amino acids, iron (stored as ferritin), vitamin B12, and folic acid are essential for erythropoiesis.

  • RBC Lifespan and Destruction

    Live 100-120 days; old RBCs are phagocytized in spleen; hemoglobin is recycled.

  • Anemia

    Condition with low O2-carrying capacity due to blood loss, decreased RBC production, or increased RBC destruction.

  • Sickle-Cell Anemia

    Genetic disorder with mutated hemoglobin S causing crescent-shaped RBCs that rupture easily and block vessels.

  • Leukocytes (WBCs)

    Complete cells with nuclei; defend against disease; classified as granulocytes or agranulocytes.

  • Granulocytes

    Include neutrophils, eosinophils, basophils; contain cytoplasmic granules; phagocytic.

  • Neutrophils

    Most abundant WBCs (50-70%); multilobed nucleus; kill bacteria via respiratory burst.

  • Eosinophils

    2-4% of WBCs; bilobed nucleus; combat parasitic worms; involved in allergies.

  • Basophils

    Rarest WBCs (0.5-1%); contain histamine which promotes inflammation and attracts other WBCs.

  • Agranulocytes

    Include lymphocytes and monocytes; lack visible granules; important in immunity and phagocytosis.

  • Lymphocytes

    25% of WBCs; large nucleus; T cells attack infected cells; B cells produce antibodies.

  • Monocytes

    3-8% of WBCs; largest WBC; differentiate into macrophages; phagocytic and activate lymphocytes.

  • Platelets

    Cell fragments from megakaryocytes; contain clotting chemicals; form platelet plugs to stop bleeding.

  • Hemostasis Steps

    1. Vascular spasm (vasoconstriction)
    2. Platelet plug formation
    3. Coagulation (fibrin clot formation)

  • Coagulation Pathways

    Intrinsic pathway triggered by blood factors; extrinsic pathway triggered by tissue factor; both activate factor X.

  • Common Pathway of Coagulation

    Thrombin converts fibrinogen to fibrin; fibrin mesh stabilizes clot; factor XIII cross-links fibrin.

  • Blood Clotting Factors

    Plasma proteins numbered I to XIII; vitamin K required for synthesis of some factors.

  • ABO Blood Groups

    Based on presence of A and/or B antigens on RBCs; antibodies in plasma react against absent antigens.

  • Rh Blood Group and Hemolytic Disease

    Rh– mother exposed to Rh+ fetus blood can form antibodies causing hemolytic disease in subsequent Rh+ pregnancies; prevented by RhoGAM.