What is the primary result of expiration?

The primary result of expiration is the expulsion of air from the lungs. During this process, the muscles involved in respiration, particularly the diaphragm and the intercostal muscles, relax after contracting during inhalation. This relaxation causes the thoracic cavity’s volume to decrease, which leads to an increase in pressure within the lungs compared to atmospheric pressure. As a result, air is pushed out of the lungs through the trachea and out into the environment.

This mechanism allows for the removal of carbon dioxide, a waste product of metabolism, and is an essential part of the respiratory cycle. The action of expiration is vital for maintaining proper gas exchange and ensuring that the body's cells receive adequate oxygen while expelling carbon dioxide efficiently. Understanding this process is critical for recognizing how the body manages respiratory function and homeostasis.