Transport of Oxygen and Carbon Dioxide

Transport of Oxygen from the Lungs to the Body Tissues

  • Oxygen Transport:
    • By diffusion from alveoli to pulmonary capillaries.
    • Alveolar PO₂ = 104 mm Hg; Venous end PO₂ = 40 mm Hg.

Uptake of Oxygen During Exercise

  • Increased Oxygen Demand:
    • Up to 20 times during strenuous exercise.
    • Enhanced diffusion due to increased surface area and ideal ventilation.

Transport of Oxygen in Arterial Blood

  • Hemoglobin Role:
    • 97% of oxygen is transported by hemoglobin; 3% dissolved in plasma.

Diffusion of Oxygen Into Tissue Fluids

  • Capillary PO₂ Changes:
    • Arterial: PO₂ = 95 mm Hg; Venous: PO₂ = 40 mm Hg.

Tissue Oxygen Regulation

  • Factors Affecting Tissue PO₂:
    • Balance of oxygen transport rate and oxygen consumption by tissues.

Diffusion of Carbon Dioxide

  • CO₂ Transport:
    • From tissue cells to capillaries and from pulmonary capillaries to alveoli.
    • Arterial end PO₂ = 45 mm Hg; Alveolar PO₂ = 40 mm Hg.

Factors Influencing Hemoglobin Function

  • Oxygen-Hemoglobin Dissociation Curve:
    • Relationship between PO₂ and hemoglobin saturation; sigmoidal shape due to cooperative binding.
    • Affinity affected by pH, CO₂ levels, temperature, and BPG.

Metabolism of Oxygen by Cells

  • CO₂ Transport Forms:
    • Bicarbonate, carbamino compounds, and dissolved gas.
    • Majority of CO₂ transported as bicarbonate (70%).

Haldane Effect

  • Deoxygenated hemoglobin binds CO₂ more efficiently than oxygenated hemoglobin, promoting CO₂ release in lungs.

Summary of CO₂ Transport

  • Transport Methods:
    • Dissolved, bound to proteins, and as bicarbonate.
    • Chloride shift facilitates bicarbonate transport in exchange for chloride ions.