Chapter 13: Alterations in Oxygen Transport

Blood Composition

• Total Blood Volume:

  • Men: ~75 ml/kg
  • Women: ~66.5 ml/kg
  • Accounts for 7-8% body weight (~5-6 liters)

• Components:

  • Cellular Components (45%):
    • Red Blood Cells (RBCs)
    • White Blood Cells (WBCs)
    • Platelets
  • Plasma (55%):
    • 92% water
    • 7% plasma proteins (Albumin, Globulin, Fibrinogen)
    • Contains electrolytes, hormones, enzymes, nutrients

Functions of Blood Cells

• Red Blood Cells:

  • Oxygen transport
  • Carbon dioxide removal
  • Buffering changes in pH

• White Blood Cells:

  • Immune defense

• Platelets:

  • Clotting

Hemoglobin

• Found in RBCs
• Composed of:
  • Two alpha chains
  • Two beta chains
  • Iron-containing heme group
• Carries oxygen (up to 4 molecules per RBC)
• Average: 15g/dL of blood

Erythropoiesis (Red Blood Cell Production)

• Stimulated by low oxygen levels
• Involves erythropoietin hormone from kidneys
• Affects bone marrow to produce RBCs
• RBC lifespan: ~120 days

Anemia

• Low hemoglobin or RBCs leading to reduced oxygen-carrying capacity

• Causes:

  • Blood loss
  • Hemolysis
  • Impaired RBC production

• Symptoms:

  • Tissue hypoxia
  • Compensatory mechanisms: increased heart rate, respiratory rate

• Types:

  • Iron Deficiency Anemia: Lack of iron
  • Megaloblastic Anemia: DNA synthesis inhibition (B12, Folic Acid)
  • Aplastic Anemia: Bone marrow issues
  • Chronic Disease Anemia: Chronic inflammation, renal failure

Hemolytic Anemia

• Breakdown of RBCs
• Symptoms:
  • Jaundice
  • Dark urine
  • Enlarged spleen/liver

Sickle Cell Disease

• Cause: Point mutation in beta chain of hemoglobin
• Symptoms: Pain due to blocked capillaries, jaundice
• Treatment: Stem cell transplant, reactivation of fetal hemoglobin

Thalassemia

• Genetic defect in globin chain production
• Types:
  • Alpha Thalassemia: Reduced alpha chain
  • Beta Thalassemia: Reduced beta chain

Polycythemia

• Increase in RBCs leading to increased blood viscosity
• Causes:
  • Polycythemia Vera: Bone marrow produces too many RBCs
  • Secondary Polycythemia: Due to chronic hypoxia
  • Relative Polycythemia: Due to dehydration

Fetal Hemoglobin

• Composed of 2 alpha and 2 gamma chains
• Cannot sickle or have beta thalassemia

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Important Concepts:

• Compensatory Mechanisms in Anemia:

  • Sympathetic activation: increased heart rate, vasoconstriction
  • Increased 2,3-DPG levels reducing oxygen affinity

• Red Blood Cell Destruction:

  • Occurs in spleen, liver, bone marrow
  • Hemoglobin processed into bilirubin, conjugated in liver

• Inheritance of Sickle Cell Disease:

  • Recessive disorder: both alleles must be sickled for disease expression

Clinical Cases:

• Sickle Cell: Crisis during low oxygen situations (e.g., respiratory infections)
• Anemia Management: Erythropoietin stimulation in renal failure, nutritional supplementation for deficiency types

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This summary captures essential points about oxygen transport alterations, covering blood composition, function, key disorders, and physiological processes.