The main difference between Inspiration and Expiration is that Inspiration (inhalation) is the method of bringing air from the outside into the lungs, while Expiration (exhalation) is the method of releasing air from the lungs to the outside.

Inspiration vs. expiration

Inspiration is also known as inhalation, thought of as the process of drawing air into the lungs. Expiration, also called exhalation, is considered the process of releasing air from the lungs to the outside through the mouth or nose.

During inspiration and intake of air into the lungs, the diaphragm moves downward by contraction and becomes flat; on the other hand, during expiration, when the air leaves the lungs, the diaphragm moves upwards, relaxing and taking the shape of a dome. Also, during the inspiration process, the external intercostal muscles contract. On the other hand, the internal intercostal muscles relax; on the other hand, during the exhalation process, the external intercostal muscles relax while the internal intercostal muscles contract.

By the action of the intercostal muscles, the rib cage moves forward and outward during the inspiration process; Rather, through the action of the intercostal muscles, the rib cage moves downward and inward during the exhalation process. During inspiration or inhalation, the size of the chest cavity increases; on the other hand, during the expiration or exhalation process, the size of the thoracic cavity decreases.

Due to the increase in the volume of the thoracic cavity during the act of inspiration, the air pressure inside the lungs decreases; on the other hand, due to the decrease in the volume of the thoracic cavity during expiration, the air pressure inside the lungs increases. In the course of inspiration, air moves into the lungs, while during expiration, air leaves the lungs.

Inspiration is known as the phase of bringing air into the lungs during breathing. Inspiration is also known as the inhalation process, and it is an active process because it involves the contraction of the muscles.

Normally, in the process of regular inspiration, the two muscle groups involved are the diaphragm and the external intercostal muscles. In this process, contractions occur in the diaphragm, moving it down around the abdominal cavity and increasing the space of the chest cavity.

Meanwhile, the external intercostal muscle contracts and moves the ribs outward and upward and expands the volume or amount of the chest cavity. Furthermore, the enlargement of the chest cavity results in the intensification of the lungs due to their adhesion to the pleural fluid. As a result, this expansion of the chest cavity is the decrease in intraalveolar pressure, which is less than atmospheric pressure, and this pressure gradient results in atmospheric pressure entering the lungs.

The inspiration process is vital to bring oxygen into the blood. Normal estimated air respiration consists of 21% oxygen (O ₂ ) and 0.04% carbon dioxide (CO ₂ ). The amount of oxygen needed increases when we exercise, and this automatically increases oxygen uptake and speeds up breathing. This increased oxygen uptake is known as VO ₂ .

What is expiration?

Expiration is known as the passive process of drawing air out of the lungs. Normally, the release of air from the lungs does not require energy. So both the diaphragm muscles and the external intercostal muscles relax during expiration as the lungs draw back.

The decrease in the diaphragm and intercostal muscles results in a decrease in the volume of the thoracic cavity and an increase in interpulmonary pressure, which is higher than atmospheric pressure. As a result, ultimately, the air that is present within the lungs is released from the lungs.

1. Inspiration is known as the active process, which brings air into the lungs, while expiration is the passive method that excludes air from the lungs to the outside environment.
2. During the inspiration process, the inspired air consists of a mixture of oxygen and nitrogen; on the other hand, during the expiration process, expired air consists of the mixture of carbon dioxide and nitrogen.
3. The inspiration method is also called the inhalation process; On the other hand, the act of exhalation is also known as the expiration process.
4. During inspiration, the mass of the thoracic cavity increases, while during the process of expiration, the mass of the thoracic cavity decreases.
5. The intercostal muscles present on the outside contract and the intercostal muscles on the inside relax during inspiration, while the outer intercostal muscles during expiration relax and the internal intercostal muscles contract.
6. The function of the intercostal muscles includes the forward and outward movement of the rib cage on inspiration; on the other hand, the function of the intercostal muscles during expiration is the downward and inward movement of the rib cage.
7. In gas exchange, oxygen enters the lungs during inspiration; on the contrary, during expiration, carbon dioxide is eliminated from the lungs.

Final Thought

The above discussion concludes that inspiration is the active process due to the participation of muscle contractions. At the same time, expiration is known as a passive process, which is the involvement of muscle relaxation. Inspiration is responsible for bringing air into the lungs, while exhalation releases air from the lungs.