What happens to lung volume and pressure during inhalation?

• A. Lung volume decreases and pressure increases
• B. Lung volume increases and pressure decreases
• C. Lung volume stays constant
• D. Pressure and volume both increase

Answer: (B)

During inhalation, the diaphragm and intercostal muscles contract, leading to an increase in lung volume. As the volume of the thoracic cavity expands, the pressure within the lungs decreases according to Boyle's Law, which states that at constant temperature, the pressure of a gas is inversely related to its volume. This decrease in pressure creates a pressure difference between the atmosphere and the lungs, allowing air to flow into the lungs until the pressures equalize.

The increase in lung volume is crucial as it allows for greater air intake, facilitating gas exchange where oxygen is absorbed and carbon dioxide is expelled. This physiological process is fundamental to the mechanics of ventilation, as it ensures that the lungs can perform efficiently and effectively for respiration. Recognizing this interaction between volume and pressure can help in understanding various respiratory mechanics and disorders.