The bronchioles belong to the airways in the lungs, they are found in the extreme parts of the bronchi, in the branches of the airways in the lungs and culminate in the alveoli, which are small circular sacs where oxygen is exchanged for dioxide of carbon in the bloodstream.

They are responsible for controlling the distribution of air in the lungs . For the oxygen contained in the air to reach the lungs, it is necessary for it to pass through the tubular ducts that reach the alveoli and in this process it is responsible for eliminating germs and foreign particles that come from it, and then penetrating the structure respiratory.

What is the function of the bronchioles?

It should be known that the trachea is the one that carries the air to the bronchi, from there they pass to the bronchioles and finally to the pulmonary alveoli. That air is returned in the form of carbon dioxide by the same route that it entered. This cycle that makes up the total process of respiration is continuous.

Next, we are going to mention the most outstanding functions of this important body:

  • Its main function is to make sure that the air that enters our body supplies all the alveoli. The lungs have a large number of alveoli that are responsible for favorable gas exchange with the atmosphere.
  • They work as conductors of the air that reaches the alveoli and also participate in the metabolism of hormones and in the detoxification of various toxic substances that enter our body.
  • So that air can reach all the alveoli, the bronchioles branch out in all possible sizes to reach the entire area.
  • They serve as ducts and at the same time prepare the air before it reaches the alveoli. During this process, by inhaling the air, it moistens it and then filters out all the toxic and foreign particles.
  • All bronchioles, even the terminals, fulfill the function of decontaminating the air that enters our body. The airways are lined with layers of mucus that help maintain the necessary humidity and trap all foreign particles from the inspired air.
  • They have the property of acting as a defense mechanism, causing coughing thanks to their sensitivity to virulent chemicals.
  • The pulmonary capillary system plays an important role, since it is a blood reservoir, which also performs excellent metabolic actions.
  • They can easily change their diameter to increase or decrease the fluidity of the air. If the diameter increases suddenly, there is bronchodilation caused by adrenaline or by the sympathetic nerves in order to increase the flow of air.
  • When it is the opposite, that instead of increasing the diameter is decreased, we are talking about a bronchoconstriction that occurs due to histamine, cold air, parasympathetic nerves, irritating chemicals and other factors that can lower the level of the fluidity of the air.

Characteristics of the bronchioles

Some important features are:

  • They are small structures that are only 1 millimeter in diameter.
  • They transport all the air we breathe to the pulmonary alveoli.
  • They branch until they reach the structures where the alveolar ducts are located, these are long ducts that end up reaching the pulmonary alveoli.
  • The first part of this organ, originates the airway of a pulmonary lobe and in turn decreases the respiratory epithelium, mainly in the smaller bronchioles.
  • The sheet that covers them is a set of tissues that do not have glands, that is, it is a smooth muscle. It also does not contain cartilage, but an extensive network of elastic fiber. When the air is inhaled and the lungs are distended, the elastic fibers and the smooth muscles exert a counter force to maintain the integrity of the entire structure.
  • They have their own nervous, lymphatic and vascular trunk, which branches at the same time in all divisions of the airways.

Classification of the anatomy of bronchioles

The bronchial system, like any respiratory tract, has cilia, which are small cells that are found on the inner surface to help move air throughout the system. They can be classified as follows:

Terminal bronchioles

They are the ones that branch out from the smallest, each one of them is divided to form the respiratory bronchioles that contain the alveoli.

Respiratory bronchioles

They are the narrowest airways in the lungs and at the same time they divide into alveolar ducts. They are also those that signal the beginning of the respiratory compartment where gas exchange takes place. They constitute a more distal segment, that is, where the end of the division that conducts the air fluids of the respiratory system is marked.

Diseases that are related to bronchioles

There is a wide variety of respiratory diseases that can affect the bronchioles, this is due to their lack of cartilage, which makes them susceptible to the affection of certain conditions that can cause obstructions, infections and inflammation in the respiratory tract. Some of these diseases are:


This happens when the bronchial smooth macular tissue contracts and narrows its diameter to such an extent that it prevents adequate absorption of oxygen into the blood. The cause is due to bronchitis, asthma, influenza, respiratory infections and consequently anaphylactic shock produced by allergens. Oxygen therapy and bronchodilators can be used to treat them.


It is caused by inflammation of the bronchioles by a respiratory syncytial virus. This pathology occurs mainly between the first 3 and 6 months of age in children with symptoms such as strong cough and respiratory deficiency, which can be treated with fluid treatments, oxygen supply and nutrition through intravenous lines or by middle of gastric tubes.

Obliterative bronchiolitis

This disease consists of a severe chronic obstruction in the lower part of the airways, it is a rare disease of high severity that affects mostly adults.

It can appear after a viral infection with frequent symptoms such as coughing and great difficulty breathing, if the situation worsens, a lung transplant may be needed.


It is an inflammatory disease of the airways, which includes reversible airflow obstruction, bronchospasm, shortness of breath, episodes of wheezing, a feeling of tightness in the chest, and constant coughing. To treat this condition, it can be done through bronchodilators, since they manage to widen the airways.

What are alveoli and what is their function?

They are small muscles in the shape of air sacs, which make up the last part of the airways. They have the ability to provide the benefit of the exchange of oxygen for carbon dioxide through the membranes of the pulmonary alveoli.

The main function of the alveoli, as we already mentioned, is to exchange carbon dioxide for oxygen. The tissues it comprises also perform important functions such as the production of enzymes, hormones and lung activation.

The alveolus is the place where inhaled substances are concentrated and in turn is where they will be processed, some are drugs, pathogens and some other chemical substances. These structures are bordered by capillaries that carry blood.

These begin to work once the air enters through the nostrils. That air will travel a long way through some organs found in the respiratory system. These organs include the nasal passages, pharynx, larynx, trachea, main bronchi, small bronchi, bronchioles, and the air sacs that are the alveoli.

Inhaled air contains oxygen, which is absorbed by the blood and then flows through the capillaries and then passes into the circulatory system to complete the cycle of gas exchange.

Bronchiole conclusion

To conclude, it can be said that these small branches of the bronchi have the ability to participate in the oxygenation process of the respiratory system and that the air can reach all parts of the lungs.

This process is based on the exchange that provides oxygen to the blood and removes the carbon dioxide produced in the body by cellular metabolism, that is, the oxygen we inhale is transported through various conduits that reach the alveoli where it is possible to purify the blood of toxic gases that can affect our respiratory system.

Samantha Robson
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Dr. Samantha Robson ( CRN: 0510146-5) is a nutritionist and website content reviewer related to her area of ​​expertise. With a postgraduate degree in Nutrition from The University of Arizona, she is a specialist in Sports Nutrition from Oxford University and is also a member of the International Society of Sports Nutrition.

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