What happens to the chest cavity as the diaphragm and intercostal muscles relax?

When the diaphragm and intercostal muscles relax, the chest cavity decreases in size. This process is essential for exhalation. The diaphragm, which is a dome-shaped muscle at the base of the thoracic cavity, plays a key role in breathing by contracting to create a vacuum that pulls air into the lungs during inhalation. When it relaxes, it returns to its original dome shape, which decreases the volume of the chest cavity. The intercostal muscles, located between the ribs, also contribute by relaxing and allowing the ribcage to drop down and inward, further reducing the space within the chest cavity.

As the size of the chest cavity decreases, the pressure within the cavity increases, creating a pressure gradient that forces air out of the lungs and into the atmosphere, a process known as exhalation. This is a natural part of the respiratory cycle, which alternates between inhalation (drawing air in) and exhalation (pushing air out).