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 alveolarpartial pressure 2
hypoventilation hyperventilation O2 Transport
100 healthy O2 80
60 diseased
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.