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Gas Exchange and Transport in Respiratory System

Explore the mechanisms of oxygen and carbon dioxide transport, role of hemoglobin, regulators of respiration and circulation coordination, gas exchange in lungs and tissues, diseases related to exchange, and factors modifying hemoglobin oxygen transport. Figure illustrations aid in visualizing concepts.

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Gas Exchange and Transport in Respiratory System

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  1. Chapter 18 Gas Exchange and Transport

  2. About this Chapter • Getting CO2 & O2 dissolved for transport • How oxygen is transported, role of hemoglobin • How carbon dioxide is transported • Regulators that sense and coordinate respiration with circulation for gas transport

  3. Overview of Respiratory Exchange Figure 18-1: Overview of oxygen and exchange and Transport CO2

  4. Solubility of Gasses • Pressure gradient: lower at high altitudes • Temperature: constant in warm blooded humans • Solubility (solute & solvent): O2 or CO2 in water Figure 18-2: Gases in solution

  5. Gas Exchange in the Lungs and Tissues: Oxygen • Diffusion through alveolar thin cells • Down diffusion gradient • Higher in alveoli • Lower in blood • Diffusion from blood • Also down gradient • To ECF • To tissue cells (convert O2 to CO2)

  6. Gas Exchange in the Lungs and Tissues: Oxygen Figure 18-3a: Gas exchange at the alveoli and cells

  7. Gas Exchange in the Lungs and Tissues: Carbon Dioxide • Diffusion out of cells (down diffusion gradient) • Into blood • Buffer role • Conversions: • Plasma • Bicarbonate • On Hb • Into alveolus & expiration

  8. Gas Exchange in the Lungs and Tissues: Carbon Dioxide Figure 18-3b: Gas exchange at the alveoli and cells

  9. Movement of Gases in Body

  10. Alveolar Exchange and Diseases Related to Exchange • Wet surface • Thin epithelia • Little ECF • Diseases: • Emphysema • Fibrotic Lung • Pulmonary edema • Asthma

  11. Alveolar Exchange and Diseases Related to Exchange Figure 18-5: Oxygen diffuses across the alveolar and endothelial cells to enter the plasma

  12. Diseases of the Lung Figure 18-4: Pulmonary pathologies that affect alveolarventilation and gas exchange

  13. Gas Transport in the Blood: Oxygen • 2% in plasma • 98% in hemoglobin (Hb) • Blood holds O2 reserve Figure 18-6: Summary of oxygen transport in the blood

  14. Gas Transport in the Blood: Oxygen Figure 18-7 : The role of hemoglobin in oxygen transport

  15. Hemoglobin Transport of Oxygen: Disassociation Curve • 4 binding sites per Hb molecule • 98% saturated in alveolar arteries • Resting cell PO2 = 40 mmHg • Working cell PO2 = 20 mmHg • More unloaded with more need • 75% in reserve at normal activity

  16. Hemoglobin Transport of Oxygen: Disassociation Curve Figure 18-8: Oxygen-hemoglobin dissociation curve

  17. Factors that Modify Hb Transport of Oxygen • Bohr effect: pH  causes  O2 binding -releasing it •  2,3 DPG decreases O2 binding to hemoglobin (response to high altitude) •  PCO2 decreases O2 binding–releasing it • (Temperature affects the curve but doesn't vary in humans)

  18. Factors that Modify Hb Transport of Oxygen Figure 18-9: Physical factors alter oxygen binding to hemoglobin

  19. Summary of Oxygen Transport • How many of these choices are likely to be variable? Figure 18-12: Factors contributing to the total oxygen content of arterial blood

  20. Gas Transport in the Blood: Carbon Dioxide • Excess CO2 in blood (Hypercapnia) • Leading to: acidosis, CNS depression & coma • 7% in plasma, 23% bound to Hb • 70% as HCO3- acts as a buffer [H+]

  21. Gas Transport in the Blood: Carbon Dioxide Figure 18-13: Carbon dioxide transport in the blood

  22. Review of Respiratory Exchange & Transport Figure 18-14: Summary of gas transport

  23. Regulation of Ventilation: Central pattern generator • Integrates input from cortex, limbic & chemoreceptors • Rhythmic contractions of ventilation

  24. Regulation of Ventilation: Central pattern generator Figure 18-15: Reflex control of ventilation

  25. Regulation of Ventilation: Pons Center Figure 18-16: Rhythmic breathing

  26. Regulation of Ventilation: Chemoreceptors • Carotid & aortic bodies: O2, CO2 & H+ receptors • Medullary CO2 receptor • Low [O2], high [CO2] & low pH  ventilation Figure 18-17: Carotid body oxygen sensor releases neurotransmitter when decreases PO2

  27. Regulation of Ventilation: Chemoreceptors Figure 18-18: Central chemoreceptor monitors in cerebrospinal fluid

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