8) Dalton’s Law & Gas Exchange

• What does Dalton’s Law state?

• The total pressure of a gas mixture equals the sum of the partial pressures of each individual gas.

• What is a partial pressure?

The pressure exerted by a single gas in a mixture, proportional to its concentration.

• Why are partial pressures important in respiration?

They determine the direction of gas diffusion across the alveolar-capillary membrane.

• Which gases are most relevant in respiratory physiology?

• Oxygen (O₂) and Carbon Dioxide (CO₂).

•  What drives oxygen diffusion into blood from alveoli?

•  The higher partial pressure of O₂ in alveoli compared to pulmonary capillary blood.

• What drives carbon dioxide diffusion out of blood into alveoli?

• The higher partial pressure of CO₂ in pulmonary capillary blood compared to alveoli.

• What is the role of the respiratory membrane in gas exchange?

• Provides a thin barrier for efficient diffusion of O₂ and CO₂ between alveoli and blood.

• How does Dalton’s Law connect to clinical relevance?

•  Explains hypoxia and hypercapnia when partial pressure gradients are altered (e.g., lung disease, altitude).

• What is the normal partial pressure of oxygen in alveoli?

•  About 104 mmHg.

• What is the normal partial pressure of carbon dioxide in alveoli?

• About 40 mmHg.