Difference Between Inhalation and Exhalation

Inhalation vs Exhalation

Respiration is the process of exchanging oxygen and carbon dioxide between the cells of the body and external environment. According to physiology of the respiratory system, the process of respiration can be divided into two types; cellular respiration and external respiration. The cellular respiration includes the intracellular metabolic processes take place within the mitochondria. External respiration is the entire process of exchanging oxygen and carbon dioxide between the external environment and body cells. However, the respiratory system does not involve in all steps of respiration, but only involve in the initial steps including the ventilation of exchange of gasses between the lungs and blood. The rest of the steps is carried out by the circulatory system that includes the transportation of oxygen and carbon dioxide between the lungs and tissues via blood, and diffusion of gasses across the systemic capillaries. Inhalation and exhalation are the processes of ventilation (pulmonary ventilation), which govern the movement of air between the environment and alveoli in lungs. 

Difference Between Inhalation and Exhalation

Inhalation and Exhalation




Inhalation is an active process of which a person takes air into the body through the mouth and nose and pushes the air into the lungs. Inhalation is controlled by the brain. During the process of inhalation, the diaphragm and intercostal muscle contractions cause to enlarge the thoracic cavity. This creates a slight vacuum condition due to decreasing air pressure in lungs. Due to the pressure gradient between the atmosphere and thoracic cavity, air moves into lungs via trachea. When the air pressure equalizes, the inhalation stops.


Exhalation is the process of moving out of air from the lung to the outer atmosphere during ventilation. It is a passive process which does not involve muscle contractions. Although it is passive, it can be done actively by contracting the muscles of the wall of the chest and abdomen. During the process of exhalation, the diaphragm and intercostal muscle relax, causing thoracic cavity to decrease in size. It eventually creates a high pressure in the lung due to the reduction of volume and thus the resulted pressure gradient causes air to move out from the lungs through the trachea to atmosphere.

What is the difference between Inhalation and Exhalation?

• Inhalation is the intake of air into lungs, whereas exhalation is the pushing out of air from lungs.

• Inhalation is an active process, whereas exhalation is a passive process.

• Exhalation occurs followed by the inhalation.

• The diaphragm and intercoastal muscle contract during the inhalation, while they relax during the exhalation.

• Inhalation causes to increase the air pressure in the thoracic cavity, whereas exhalation causes to increase it.

• Volume of lung increases during the inhalation, while it decreases during the exhalation.


Read more:

1. Difference Between Lung Volume and Lung Capacity

2. Difference Between Pulmonary and Systemic Circuit

3. Difference Between Aerobic Respiration and Anaerobic Respiration