Determine the percent composition of air in the lungs from the following composition in partial pressures: PN2 = 573 mmHg, PO2 = 100 mmHg, PCO2 = 40 mmHg, and PH2O = 47 mmHg; all at 37 °C and 1 atm pressure.

Partial pressure refers to the pressure exerted by a single gas in a mixture of gases. It is a crucial concept in understanding gas behavior, as each gas in a mixture contributes to the total pressure according to its mole fraction. In this context, the partial pressures of nitrogen, oxygen, carbon dioxide, and water vapor in the lungs are used to determine their respective contributions to the overall composition of air.

Percent composition is a way to express the concentration of each component in a mixture as a percentage of the total. It is calculated by dividing the partial pressure of each gas by the total pressure of the gas mixture and multiplying by 100. This concept is essential for determining how much of each gas is present in the air within the lungs, which is vital for understanding respiratory physiology.

Dalton's Law states that the total pressure of a gas mixture is equal to the sum of the partial pressures of its individual gases. This principle allows us to calculate the total pressure in the lungs by adding the partial pressures of nitrogen, oxygen, carbon dioxide, and water vapor. Understanding this law is fundamental for analyzing gas mixtures and their behaviors in various conditions, such as in the human respiratory system.