Blood notes

FUNCTIONS OF BLOOD

  • Delivery & Transport:

    • Oxygen (O2) and Nutrients: Essential for cellular metabolism.

    • Wastes and Carbon Dioxide (CO2): Removal from tissues.

    • Hormones: Transport of signaling molecules throughout the body.

  • Regulation:

    • Body temperature: Maintains thermal homeostasis.

    • pH: Maintains the acid-base balance (normal range: 7.35 - 7.45).

    • Fluid volume: Regulation of blood volume and pressure.

  • Protection:

    • Hemostasis: Prevents excessive bleeding through clotting mechanisms.

    • Immunity: Defends against pathogens through various immune responses.

COMPOSITION OF BLOOD

  • Approx. 5 L of fluid connective tissue (CT) composed of:

    • Formed Elements: Red blood cells (RBCs), white blood cells (WBCs), and platelets.

    • Plasma: The fluid extracellular matrix (~50% of blood volume).

DEMONSTRATION OF BLOOD COMPONENTS

  • Blood can be drawn into a tube containing anticoagulants (e.g., EDTA) and then centrifuged to separate components based on density.

PLASMA

  • The complex fluid portion of blood, accounting for approximately 50% of the total blood volume.

    • Composition:

    • ~90% H2O

    • ~10% Solutes

    • Serum: The fluid portion of clotted blood.

NORMAL pH of BLOOD

  • Normal: 7.35 - 7.45

  • Acidosis: pH < 7.35

  • Alkalosis: pH > 7.45

SOLUTES IN PLASMA

  • Plasma Proteins: Most synthesized in the liver.

    • Albumin: Major protein, maintains oncotic pressure and transports various substances (e.g., fatty acids).

    • Globulins: Include transport proteins and immunoglobulins (IgA, IgG, IgM).

    • Fibrinogen: Converts to fibrin during clotting.

  • Other Solutes:

    • Non-protein nitrogenous substances (urea, uric acid, creatinine)

    • Nutrients (glucose, amino acids, fatty acids)

    • Electrolytes (Na+, K+, Ca²+, Cl-, HCO3-)

    • Gases (O2, CO2)

    • Hormones

PLASMA PROTEINS

  • Albumin:

    • Most abundant protein, ~60% of total plasma proteins. Functions include maintaining osmotic pressure.

  • Globulins:

    • Heterogeneous group of proteins.

    • γ-Globulins (Immunoglobulins): Synthesized by WBCs, involved in immunity.

  • Clotting Proteins: Include fibrinogen and prothrombin (factors I and II, respectively).

BLOOD CLOTTING FACTORS (TABLE 17.3)

  • Factor I: Fibrinogen - converted to fibrin.

  • Factor II: Prothrombin - converted to thrombin.

  • Factor III: Tissue factor - initiates coagulation cascade.

  • Factor IV: Calcium ions (Ca²+) - necessary for all stages of the coagulation process.

  • (Further factors listed - detailing origin, function, and pathway)

NON-PROTEIN NITROGEN SOURCES

  • Urea/BUN: Product of amino acid breakdown; important renal function indicator.

  • Uric Acid: From nucleic acid metabolism; elevated levels can lead to gout.

  • Creatinine: Derived from creatine phosphates; also a measure of renal function.

NPN IMPORTANCE

  • Indicators of kidney function; elevated levels suggest renal impairment.

ELECTROLYTE LEVELS

  • Abnormalities:

    • Hypernatremia: Na+ > 145 mEq/L; can result from dehydration.

    • Hyponatremia: Na+ < 135 mEq/L; related to water retention or loss.

    • Hyperkalemia: K+ > 5.5 mEq/L; causes cardiac disturbances.

    • Hypokalemia: K+ < 3.5 mEq/L; can lead to muscle weakness.

    • Hypercalcemia/Hypocalcemia, Hyperphosphatemia/Hypophosphatemia, etc.

ERYTHROCYTE CHARACTERISTICS

  • Comprise ~45% of blood volume; specialized for O2 and CO2 transport.

  • Structure:

    • Biconcave shape, enhancing gas exchange and reducing friction.

    • Contains hemoglobin:

    • Globin: 2 alpha and 2 beta chains

    • Heme group: Contains iron, binding O2 and CO2.

ERYTHROCYTE LIFE CYCLE

  • Average lifespan of RBCs: ~120 days

  • Life cycle includes stages from hemocytoblast to proerythroblast to normoblast and finally reticulocyte before maturity.

REGULATION OF ERYTHROPOIESIS

  • Erythropoietin (EPO) released by kidneys in response to hypoxia stimulates RBC formation.

  • Chronic high altitude will increase EPO release and enhance erythropoiesis.

ANEMIA TYPES AND CHARACTERISTICS

  • Hemorrhagic Anemia: Acute/chronic blood loss (e.g., injury, ulcer).

  • Hemolytic Anemia: Related to destruction of RBCs (infections, transfusion reactions).

  • Sickle Cell Anemia: Caused by HbS, leading to RBC sickling and blockage of capillaries.

  • Thalassemia: Genetic disorders leading to varying severity of anemia.

LEUKOCYTES/WBCs

  • Function to fight infections, destroy damaged cells, and modulate immune response.

  • Normal WBC Count: ~4,800-10,800 cells/mm³.

  • Types include granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes, lymphocytes).

HEmostasis and Coagulation Processes

  • Phases of Coagulation: Vascular spasm, platelet plug formation, and coagulation cascade following tissue injury.

  • Thromboxane A2 promotes platelet aggregation and vasoconstriction; occurs via platelet release mechanisms following endothelial injury.

  • Clot Formation: Involves a cascade of clotting factors leading to fibrin formation, ultimately stabilizing the clot.

ABNORMAL BLEEDING DISORDERS

  • Thrombocytopenia: Defined as a deficiency in platelet numbers, potentially due to cancers or autoimmune diseases.

  • Hemophilia: Genetic conditions leading to deficiencies in coagulation factors, affecting the blood clotting ability.

DIETARY REQUIREMENTS FOR ERYTHROPOIESIS

  • B Vitamins: Folic acid and B12 are crucial for DNA synthesis necessary for erythropoiesis.

  • Iron: Essential for hemoglobin production; deficiencies lead to hypochromic anemia.

CLOT PREVENTION AND ANTICOAGULANTS

  • Natural inhibitors include prostacyclins, antithrombin III, and heparin.

  • Medications such as aspirin and vitamin K inhibitors serve in preventing unwanted clot formation during treatment protocols.

  • Laboratory Tests for Coagulation: Prothrombin time (PT) and partial thromboplastin time (PTT) assess health and functionality of blood clotting processes.