07/08/2026
The process of breathing, also known as pulmonary ventilation, is the movement of air into and out of the lungs. It occurs in two main phases: inhalation and exhalation. During inhalation, the diaphragm contracts and moves downward while the external intercostal muscles lift the rib cage upward and outward. This increases the size of the thoracic cavity, causing pressure inside the lungs to drop below atmospheric pressure. As a result, air flows into the lungs.
Once air reaches the alveoli, oxygen moves across the thin alveolar-capillary membrane into the bloodstream.
At the same time, carbon dioxide moves from the blood into the alveoli to be removed from the body.
This gas exchange is essential for maintaining normal oxygen levels and acid-base balance.
During exhalation, the diaphragm relaxes and moves upward, while the rib cage returns to its resting position.
This decreases the size of the thoracic cavity, increases pressure inside the lungs, and pushes air out. In quiet breathing, exhalation is mostly passive. However, during exercise or respiratory distress, additional muscles help force air out more effectively. Overall, breathing allows the body to take in oxygen and eliminate carbon dioxide. Hope you have learned something new here? Don't forget to follow if you want to see more of our resources. Are you a graduate preparing for your NBRC board exams? Worry no more join us here to guarantee your success with effective study Guidance!