When volume increases in the thoracic cavity, then the _____ decreases.
The correct answer and explanation is:
When the volume increases in the thoracic cavity, then the pressure decreases. This relationship is based on Boyle’s Law, which states that the pressure of a gas is inversely proportional to its volume when the temperature is held constant. In the context of the human respiratory system, this principle is crucial during the process of inhalation.
The thoracic cavity is the chamber in the body that houses the lungs and is bordered by the rib cage, diaphragm, and sternum. During the process of breathing, the diaphragm contracts and moves downward, while the intercostal muscles contract to lift the ribs upward and outward. This action increases the volume of the thoracic cavity.
As the thoracic cavity’s volume increases, the space available for the lungs to expand also increases. Since the volume is now greater, the air pressure inside the lungs becomes lower than the atmospheric pressure outside the body. This pressure difference causes air to flow into the lungs, moving from the higher-pressure environment outside to the lower-pressure environment inside the lungs. This process is essential for the inhalation of oxygen.
Conversely, when the volume of the thoracic cavity decreases (as the diaphragm relaxes and moves upward, and the ribs return to their resting position), the pressure inside the lungs increases, which forces air out of the lungs (exhalation). This cycle of increasing and decreasing volume and pressure allows the body to take in oxygen and expel carbon dioxide.
Understanding the relationship between volume and pressure in the thoracic cavity helps explain how the lungs facilitate respiration. It is a key concept in both basic physiology and respiratory mechanics.