The Function of Bronchi, Location, Structure and Diagram

Bronchi Definition:

Do you have any brief idea about “What is bronchi?”. Well, it is a plural form of bronchus. Here it becomes pertinent to define bronchus. A bronchus, on the other hand, can be defined as either of the two branches of trachea which lead directly to the lungs.

So, the appendix definition makes it clear that a bronchus is actually a sub-division of the windpipe. The trachea or windpipe serves as a passage for airflow between mouth or larynx and the lungs.


Structurally composed of cartilaginous material, the air passages show a significant amount of flexibility. This flexibility, in turn, substantially contributes to their functioning efficiency.

Any abnormal condition in the structure gives rise to great disturbance and severe symptoms of the respiratory system. But a number of remedial strategies are available for almost all of such disorders.

Bronchi Structure:

The bronchi structure is easy to understand. The dichotomous branching of the tracheal tube at the point of sternal angle gives rise to two comparatively smaller tubes, viz. the left and the right bronchi (singular: bronchus).

Each of the pair of these branches extends below the 5th thoracic vertebrae to meet either of the lungs.

However, it is not the ultimate division of windpipe. Further branching takes place deeper into the lungs with the gradual decrease in the diameter of the bronchial lumen. It finally reaches the size of smallest airways, called respiratory sacs.

Bronchi Parts:

What do you know about the bronchi parts? Let’s learn it here. The mainstem divisions of windpipe are two in number each penetrating into bilaterally symmetrical sides of the human body.

However, you can easily witness certain differences in the structure of the left and right bronchus. For example, the right main bronchus is more vertical, wider and shorter in length than the left main bronchus.

As a consequence of the further division of the left mainstem bronchus, two lobar bronchi emerge. While right major bronchus gives rise to three lobar bronchi.

The segmentalinic or tertiary bronchial tubes form from the subdivision of lobar bronchus. Here a septum of connective tissue separates them from one another.

Secondary Bronchi:

There are gradual divisions and sub-divisions in the air passages branching from trachea. So there are different names for tubes of different sizes. In this regard, the second important division is that of secondary bronchus.

The secondary bronchi definition puts it as: the branching of a bronchus into smaller air passages results in the formation of secondary bronchi. The ‘lobar bronchi’ is another name for the secondary bronchi.

Secondary Bronchi Function:

The main secondary bronchi function is to serve as an intermediary path between the primary bronchus and the tertiary bronchus. The air coming from the mouth enters larynx or the voice box. From here, it heads towards the small air sacs of lungs through the trachea and its gradual sub-divisions. The secondary branches are three in number. Their job is to deliver oxygen to the superior, middle and inferior lobes of the right lung.

Tertiary Bronchi:

From the term “tertiary bronchi”, one can easily guess that it results from the further branching of the secondary bronchus. Obviously, in this case, the diameter of the resulting air canals would be smaller. The division does not stop here – it continues till you get even smaller tubes. Can you guess what comes next? Well, these are the bronchioles. In other words, the tertiary branches develop a link between the secondary branches and the bronchioles.

They are usually 10 in number in each of the lung lobes, but they may also fuse with one another due to the developmental processes in the region. Smooth muscles are always present along the D-shaped incomplete rings of the bronchial tubes which are, in turn, composed of hyaline cartilage.


Bronchioles result from the further subdivision of tertiary bronchi. Consequently, these air passages have even smaller diameter for the lumen. You can also call them bronchioli. Concerning the bronchioles function, they lie in the conducting zone of your respiratory system and form an important part of it. At this stage, the branches no longer contain cartilage in their walls. Meanwhile, the submucosal glands are also absent. Finally, the bronchioles open into the alveoli or air sacs. It is here where the gaseous exchange takes place.

Bronchi Function:

Though their walls do not let the respiratory gases pass across them, the bronchial canals are the main channels for the passage of airstream towards the major respiratory organs. They also make significant contribution to the protection of lungs against germs and dirt particles. The germs and dirt particles are trapped in the mucous lining of the lumen.

Afterwards, there is upward expelling and removal of such unwanted things out of the windpipe with the help of ciliated cells. The hyaline cartilaginous material that forms the D-shaped incomplete rings of the bronchial walls prevents the tubes from collapsing and obstructing the flow of air.

However, with the passage of time as you grow older, this soft flexible material becomes a hard and rigid bony substance. Consequently, it reduces the overall efficiency of the structure. The alveolar sacs (or alveoli) form as a result of many subdivisions of the mainstem bronchi. And these are the places where the exchange of respiratory gases takes place.

Diseases of Bronchi

There are a number of respiratory disorders that affect the subdivisions of windpipe at different levels, i.e. bronchi, bronchioles and alveoli or respiratory sacs. For example, bronchitis – as the very name suggests – is the inflammatory disorder of bronchi. It may occur in either of the two major forms, viz. chronic and acute one.

Chronic bronchitis results from the prolonged exposure to the irritants and smoking habits. While acute form is the result of the bacterial and viral infections. As a response to the allergens (antigens producing abnormally vigorous immune response), hyperactivity occurs in the bronchial canals. People call this condition as asthma.

Because of its vertical position, the right main bronchus is more vulnerable to the disorders. It is because the germs and dust particles present in the atmospheric air get entry into the right lung quite easily. Over there, they cause mild or severe medical conditions.

About the Author

Posted by: M. Isaac / Senior writer

A graduate in biological sciences and a PhD scholar (NCBA&E University, Lahore), M. Isaac combines his vast experience with a keen and critical eye to create practical and inherently engaging content on the human body. His background as a researcher and instructor at a secondary school enables him to best understand the needs of the beginner level learners and the amateur readers and educate them about how their body works, and how they can adopt a healthier lifestyle.

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