Blood - Tagged

Chapter: Blood

I. Blood Composition

  • Components of Blood:

    • Plasma

    • Formed Elements:

      • Erythrocytes (Red Blood Cells, RBCs)

      • Leukocytes (White Blood Cells, WBCs)

      • Platelets

II. Blood Volume and Characteristics

  • Hematocrit:

    • Percent of blood volume consisting of RBCs

    • 47% ± 5% for males

    • 42% ± 5% for females

  • Physical Characteristics:

    • Appearance: Sticky, opaque liquid

    • Color: Ranges from scarlet to dark red

    • pH: 7.35–7.45

    • Temperature: ~38ºC

    • Average volume: 5–6 L for males and 4–5 L for females

III. Functions of Blood

  1. Distribution:

    • Oxygen and nutrients to cells

    • Metabolic wastes to lungs and kidneys for elimination

    • Hormones from endocrine organs to target organs

  2. Regulation:

    • Body temperature by heat distribution

    • pH through buffer systems

    • Fluid volume in circulatory system

  3. Protection:

    • Against blood loss via clot formation (via plasma proteins and platelets)

    • Against infection (via antibodies, complement proteins, and WBCs)

IV. Blood Plasma

  • Composition:

    • 90% Water

    • Proteins (mostly produced by the liver):

      • 60% Albumin

      • 36% Globulins

      • 4% Fibrinogen

    • Contains various substances:

      • Nitrogenous by-products (lactic acid, urea, creatinine)

      • Nutrients (glucose, carbohydrates, amino acids)

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

      • Respiratory gases (O2, CO2)

      • Hormones

V. Formed Elements

  • Characteristics:

    • Only WBCs are complete cells

    • RBCs lack nuclei and organelles

    • Platelets are cell fragments

    • Most cells survive for a few days; originate from bone marrow and do not undergo division

VI. Erythrocytes (RBCs)

  • Structure:

    • Biconcave discs, anucleate, minimal organelles

    • Packed with hemoglobin (Hb) for gas transport

    • Contains spectrin for shape maintenance and flexibility

  • Functions:

    • Dedicated to respiratory gas transport

    • Hemoglobin structure includes:

      • Two alpha and two beta chains

      • Each heme can bind one O2 molecule (4 O2 per Hb)

VII. Hematopoiesis

  • Definition: Blood cell formation (hemopoiesis) occurs in the red bone marrow

  • Stimulation: Governed by hormonal controls and adequate supplies of nutrients

VIII. Erythropoiesis Regulation

  • Hormonal Control: Erythropoietin (EPO) released by kidneys in response to hypoxia

  • Effects of EPO:

    • Stimulates RBC production, increasing reticulocyte count

    • Testosterone enhances EPO production, resulting in higher RBC counts in males

IX. Erythrocyte Disorders

  • Anemia: General term for low O2-carrying capacity in blood

  • Causes:

    1. Insufficient erythrocytes (e.g., hemorrhagic, hemolytic, aplastic anemia)

    2. Low hemoglobin content (iron-deficiency, pernicious anemia)

    3. Abnormal hemoglobin (thalassemias, sickle-cell anemia)

  • Polycythemia: Excess RBCs leading to increased blood viscosity

    • Causes include polycythemia vera (bone marrow cancer) and secondary polycythemia (high altitude)

X. Leukocytes (WBCs)

  • Characteristics:

    • Make up <1% of blood volume

    • Can leave capillaries (diapedesis) and move through tissues by ameboid motion

    • Respond to infections (leukocytosis)

  • WBC Count: Normal range is 4800 – 10,800/mm3, divided into types:

    • Neutrophils (50-70%), Lymphocytes (25-45%), Eosinophils (2-4%), Basophils (0.5-1%), Monocytes (3-8%)

XI. Disorders of Leukocytes

  • Leukopenia: Abnormally low WBC count, often drug-induced

  • Leukemias: Cancerous conditions, categorized by the type of abnormal WBC

    • Acute vs chronic forms depending on severity and age group affected

XII. Platelets

  • Characteristics:

    • Small fragments of megakaryocytes involved in clotting

    • Formation regulated by thrombopoietin

  • Functions:

    • Form temporary plugs to seal blood vessel breaks

    • Maintained in an inactive state by nitric oxide and prostacyclin

XIII. Hemostasis

  • Process: Series of reactions to stop bleeding

    1. Vascular spasm

    2. Platelet plug formation

    3. Coagulation

XIV. Coagulation Phases

  1. Prothrombin Activator Formation: Triggered by either intrinsic or extrinsic pathways

  2. Conversion of Prothrombin to Thrombin: Leads to clot formation

  3. Fibrin Mesh Creation: Fibrin strands form the structural base of a clot

XV. Disorders of Hemostasis

  • Thromboembolic Disorders: Unwanted clotting; can lead to tissue death

  • Bleeding Disorders: Conditions inhibiting normal clot formation (e.g., thrombocytopenia, hemophilia)