Respiratory System: Characteristics, Parts, Functions And Diseases

Summary of the parts and functions of the nervous system of the human body, and its diseases.

Respiratory system

The respiratory apparatus or system refers to the set of organs that living beings have in order to exchange gases with the environment. This cold definition is soon postulated, but the concept is put more into perspective when we consider that oxygen is the engine of cellular work, with all that it entails.

Mitochondria (cell organelles) convert glucose and oxygen into high-energy bonds that can be stored in ATP and used by the cell for metabolism. Thus, we can fearlessly say that, together with water, the air in the environment makes life as we know it possible.

That is why to encompass the mammoth world of the respiratory system we require a multidisciplinary approach: it is not enough for us to focus on its morphology, but we must also explore what happens when it fails and the numerical data that support its importance. If you want to get a general idea about this exciting physiological conglomerate, read on.

Respiratory system: its main characteristics

According to the Royal Spanish Academy of the language, the term “system” in its most biological meaning is defined as a set of organs that intervene in some of the main vegetative functions of living beings. In this case, there is no doubt that we are facing the phenomenon of respiration, which is said soon.

To begin to dissect this web of biological networks and mechanisms, we can focus on the parts of this apparatus. Let’s go there.

Parts of the respiratory system

It is necessary to clarify that the respiratory system is composed of three different parts.

In the first place, we have an air conducting portion (nasal cavities, bronchi, bronchioles … etc), or what is the same, a series of branched tubules through which gases circulate.

Beyond this, it is also possible to distinguish a respiratory portion for gas exchange, where the more “blood” component of the system comes into play (for example, the alveoli and their capillaries are understood here). Finally, to close this triad, living beings have a ventilatory mechanism, which “pumps” the entry and exit of gases from our body (rib cage and intercostal muscles, for example).

We are facing a system of complex evolutionary origin that imitates exquisitely sophisticated machinery (or rather the other way around, since every machine is based on physical and biological processes).

This device has a series of highways and travel channels (conductive portion), a material exchange center (alveoli and associated circulatory parts) and a pumping device that exerts the necessary pressures for the “machine” to function (the muscles, rib cage and diaphragm). All of these elements are perfectly matched to maximize the individual’s energy output at any given moment.

Yes, we could present you a list with all the organs and structures associated with this device: nostrils, larynx, pharynx, trachea, lungs, diaphragm … etc, but we would be missing a lot of relevant information that you may not know. Let’s remember: to understand a system, even in a general way, we must not limit ourselves only to its physiological structures. So let’s jump into the world of breathing.


Breathing and its figures

“Respiration” is the process by which living beings exchange gases with the external environment. What not many people know is that this term has another meaning, as respiration is also considered to be the set of biochemical reactions by which some organic compounds are completely degraded, by oxidation, until they become inorganic substances. As you may have guessed, this is cellular respiration, or what is the same, the process of obtaining energy.

We are going to focus on the first of the definitions of the term: pulmonary respiration (in vertebrates, since other animals breathe through tracheae or gills). As a general concept, we can affirm that the process of inspiration and expiration is about a pressure game. Intrapleural pressure, intrathoracic volume, associated musculature, and diaphragm vary in position and functionality so that this mechanical activity can be performed without problems. How does this translate into objective figures?

  • Humans breathe in and breathe out between five and six liters of air per minute.
  • In 24 hours a healthy person inhales and exhales about 8000 liters of air.
  • In breaths as such, this translates to about 21,000 a day.
  • Through this exchange, each human contributes a little more than a kilo in weight of CO2 to the atmosphere daily.

This data puts things in perspective, right? Due to the functionality of the respiratory system, the oxygen content in the body of any living being is higher in the organs involved in this process, but it decreases throughout any arterial and venous system. This oxygen content is quantified with the partial pressure, that is, the theoretical pressure of the gas if it occupied the entire volume of the original mixture. The alveolar pressure of the pulmonary gases is 14.2 Kpa (Kilopascals).

All these facts and figures are of great interest, but all that glitters is not gold. Such a complex system requires exquisite integration of all its components, and unfortunately, this is not always the case.

Diseases of the respiratory system

We have talked about the parts of this apparatus and the respiratory process, but we cannot leave out what happens when it fails. The World Health Organization gives us the following data :

  • About 235 million people (7% of adults) suffer from one of the most common respiratory disorders: asthma.
  • In 2016 more than 400,000 people died from asthma. In the past it was estimated that 80% of deaths occur in low-income countries.
  • Chronic Obstructive Pulmonary Disease (COPD) affects more than 200 million people in the world.
  • This last data is even worse if one takes into account that various studies affirm that up to 90% of cases are not diagnosed.
  • Pneumonia is responsible for 15% of deaths in children under five years of age.

We could continue to expose data of this nature for years. Respiratory diseases can be caused by bacteria, viruses, helminth parasites, allergies, dysfunctions in the immune system, cancer, hereditary diseases and many other causes. Basically, anything that can get into the upper or lower airways can lead to pathology.

The apparent vulnerability of the respiratory system reaches such an extent that fungi can grow inside the lungs. This is the case of bronchopulmonary aspergillosis and invasive pulmonary aspergillosis, pathologies caused by the fungus of the genus Aspergillus .

Such is the lethality of this disease that, if it spreads through the patient’s organs, the mortality rate can reach more than 87%. For the relief of readers, this condition only occurs in people who are immunosuppressed or with severe respiratory conditions.

Another of the queens of respiratory tract pathologies is undoubtedly lung cancer. In Spain about 18,000 people die annually from this malignant tumor process, which corresponds to 27% of all deaths from cancer. Smoking is associated with up to 90% of deaths from lung cancer, so the recommendations are made on their own.


As we have seen, the respiratory system gives us one of lime and another of sand. On the one hand, it is an exciting device that integrates the functions of various organs and structures exactly, but on the other, its malfunction and disorders can end the patient’s life, depending on their immune situation, place of origin. and lifestyle habits.

Once again, we are not moving only in a physiological field, because beyond the tissues and structures that give shape and name to a system, there are a series of exciting numerical data that are often overlooked when addressing issues of this nature so concrete.

Bibliographic references:

  • Respiratory system, student resources of the University of Alcalá de Henares (UAH). Retrieved September 25 at
  • Lung cancer, AECC. Retrieved September 25 from % A1ncer% 20of% 20pulm% C3% B3n,% 25% 20of% 20total% 20of% 20deaths).
  • How the Lungs Work, National Heart, Lung, and Blood Institute (NIH). Retrieved September 25 at % ADgene% 20a% 20la% 20blood% 20y, to% 20make% 20possible% 20la% 20breathing% C3% B3n.
  • Chronic Respiratory Diseases, World Health Organization (WHO). Collected on September 25 at
  • Pérez-Arellano, JL, Andrade, MA, López-Abán, J., Carranza, C., & Muro, A. (2006). Helminths and respiratory system. Archives of Bronconeumology, 42 (2), 81-91.
  • The global impact of respiratory diseases, World Health Organization (WHO). Retrieved September 25 from

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