The Respiratory System - 5 Oxygen transport Jennifer Carbrey Ph.D. Department of Cell Biology image by OCAL, http://www.clker.com/clipart-26501.html, public domain Respiratory System 1. Anatomy and mechanics 2. Lung volumes and compliance 3. Pressure changes and resistance 4. Pulmonary function tests and alveolar ventilation 5. Oxygen transport 6. CO2 transport and V/Q mismatch 7. Regulation of breathing 8. Exercise and hypoxia Alveolar gas equation CO produced RQ = 2 O2 consumed Ventilation & Alveolar Gas Pressure Hypoventilation: CO2 production > alveolar ventilation (increased PCO in O2 2 arterial blood). 100 mm Hg Hyperventilation: CO2 production < alveolar ventilation (decreased PCO2 in arterial blood). 40 mm Hg CO alveolar partial pressure 2 hypoventilation hyperventilation O2 Transport 100 healthy O2 80 diseased 60 40 Pulmonary capillary Pulmonary P capillary 20 0 20 40 60 80 100 Normally, diffusion of O2 across pulmonary capillaries is always sufficient, even with exercise. % of capillary length PAO2 determines the diffusion gradients throughout the cardio-pulmonary system. Hemoglobin PO2 = PO2 PO2 < PO2 PO2 = PO2 O2 O2 O O2 O2 O2 O2 O2 O 2 O O 2 2 O2 O2 2 O2 O2 O2 O2 O2O O2 O2 O 2 O O2 2 2 O2 O2 O2 O2 O2 O O O 2 2 2 O2 O2 O2 O2 Total amount of O2 in blood depends on PO2 and amount of Hb in blood! 98-99% is O2-Hb in RBC, 1-2% is free in plasma Hemoglobin HbO2 HbO2 O2 O2 O2 O2 lung tissues O2 O2 O2-Hb Dissociation Curve arterial PO2 venous PO2 Arterial blood is 100% Saturated Venous blood is 75% saturated exercising muscle O2-Hb Binding Cooperativity: even at high altitude where PO2 = 60 mmHg Hb is 90% saturated! image by Diberri (modified), http://commons.wikimedia.org/wiki/File:Hb_saturation_curve.png, Creative Commons Attribution-Share Alike 3.0 Unported license. O2-Hb Dissociation Curve left shift right shift Hb affinity for O2 changes: “loading” (left shift) “unloading” (right shift) Near active cells, unloading due to: ** elevated PCO2, 2,3DPG, & temperature as well as low pH (acidity). image by Diberri (modified), http://commons.wikimedia.org/wiki/File:Hb_saturation_curve.png, Creative Commons Attribution-Share Alike 3.0 Unported license. Key Concepts • Alveolar PO2 is determined by the PO2 of atmospheric air, the alveolar ventilation rate, and RQ. • Oxygen transport is not limited by diffusion. • Oxygen is transported in blood by binding to Hb which increases its concentration 70-fold compared to its intrinsic solubility. .