Phases of Breathing

Breathing is the most essential process for the human organism. Although we're not always aware of it, it develops through different phases. Do you know them? In this space, we'll teach you about them.
Phases of Breathing

Last update: 18 May, 2021

Did you know there are phases to our breathing? Breathing is an essential physiological process which we’re often not even aware of. However, without it, life wouldn’t be possible. In this article, we’ll tell you what breathing consists of and what its phases are.

What is breathing?

Breathing is a physiological process inherent to living beings. Through it, we exchange gases with the environment. Oxygen, a substance necessary for all cells in the body to function properly, is introduced into the body.

Oxygen is exchanged for carbon dioxide. This gas is the result of metabolic processes that take place in the body. Cells use oxygen and, as a result, produce carbon dioxide. If it’s found in high concentrations in the body, it’s toxic and is therefore expelled to the outside world.

The entire breathing process is carried out constantly, either consciously or unconsciously. As soon as we stop breathing for a short period of time, our cells stop receiving oxygen and stop performing their function, which ultimately leads to their death.

A person breathing in fresh air.
Breathing is a vital function that we all perform consciously or unconsciously.

What are the phases of breathing?

We’re going to make two classifications. One of them will be the traditional one, which is based on the phenomena that occur and that we can see with the naked eye in a person. However, the other will be the organic classification. This will classify the processes that occur at a cellular level during respiration.

Traditional phases of respiration

As we’ve already said, this classification will be made on the basis of processes that we can observe with the naked eye. In this case, we’ll look at the movements and actions performed by the muscles in our rib cage.


In this phase, air enters the organism from the outside. It does so through the person’s nose and mouth, passing through the larynx and into the bronchi. These are the most distal part of the airway and are located inside the lungs.

In this phase, the muscles of the thorax are performing distension. This is the active phase. So, as these muscles distend, the rib cage becomes larger, expanding the lungs. Then the diaphragm descends. Therefore, the pressure in the lungs becomes lower than on the outside, and the air from the outside will enter without any problem.


In this phase carbon dioxide is expelled to the outside. This gas travels in the reverse direction to the incoming air. From the bronchi, it passes through the entire respiratory tree until it then exits through the nose or mouth. In this case, what happens is that the muscles of the rib cage return to their relaxed position.

In addition, the rib cage becomes smaller, the lungs contract and the diaphragm rises again. Thus, the pressure is greater inside the thorax than outside and the air tends to escape. This is the passive phase of breathing.

Organic phases of breathing

Organic phases of lungs.
The organic phases of respiration refer to the processes that occur at a cellular level during respiration.

These are based on phenomena that occur on a smaller scale, in the cells of our organism.

External respiration

In external respiration, gases are exchanged between the environment and the person. As we’ve said, air travels from the nose through the entire respiratory tree until it reaches the bronchi. Lastly, the pulmonary bronchi end in a structure called alveoli.

It’s in the alveoli where gas exchange actually takes place. On the one hand, this structure receives blood vessels with carbon dioxide-filled, oxygen-poor blood from the rest of the body. On the other hand, oxygen-filled ambient air arrives.

This is where the exchange takes place. The blood, specifically the red blood cells, gives up the residual carbon dioxide to the alveoli and absorbs oxygen from the outside by means of the alveoli. Then, this oxygenated blood will travel to the rest of the organism nourishing the cells of all the tissues with oxygen. The carbon dioxide, as we’ve already mentioned, will be expelled into the environment.

Internal respiration

It consists of the exchange of gases between the red blood cells and the cells. The blood arriving from the lungs, rich in oxygen, gives up oxygen to the cells due to the difference in concentration of this gas. The same is true for carbon dioxide.

In addition, the cells which have produced carbon dioxide by their metabolism, are very rich in this gas. Likewise, because of the difference in dioxide concentrations between the cells of the tissues and the red blood cells, it passes into the blood.

This oxygen-poor and dioxide-rich blood will travel to the heart, from where the heart will pump it to the lungs to re-oxygenate and repeat the process.

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  • Calais B, Traducción Supervisada Por José G, Marín L. ANATOMÍA PARA EL MOVIMIENTO-TOMO IV La respiración ® [Internet]. 2005 [cited 2020 Mar 22]. Available from:
  • Padilla Pérez J, Kowalchuk JM, Taylor AW, Paterson DH. Determinación de la cinética de la fase dos transitoria de la VO2 durante ejercicio de carga constante de intensidades moderada e intensa en hombres jóvenes. Vol. 74, Revista del Hospital Juárez de México. Medigraphic; 2007.
  •  Dipòsit Digital de la Universitat de Barcelona: Fisiología del aparato respiratorio [Internet]. [cited 2020 Mar 22]. Available from: