HOW does air enter the lungs?

Translation of page 153 – English in Medicine book

After the air passes through the trachea to the lungs, it enters two branches: one into the right lung, the other into the left embryo. Those two branches are called the main bronchi (primary bronchi). A branch is called a bronchus (bronchus). The bronchi also have surrounding cartilage, but the amount of cartilage decreases as the bronchi extend to the lungs. Immediately after the main bronchus enters the lungs. Each bronchus branches back. These new branches are called lobar bronchi (secondary bronchi). Each lobar bronchus enters one of the lobes of the lung. There are 3 lobes in the right lung and two 2 lobes in the left lung. Hence there are 5 lobar bronchi. Within the lobes of the lung, the lobar bronchi branch into segmental bronchi (tertiary bronchi).

The segmental bronchi in the lungs branch into smaller tubes called bronchioles.bronchiole). Although these bronchioles are relatively small in diameter, they play an important role in regulating the amount of air entering the lungs. The bronchioles have a thin layer of smooth muscle that contracts when less air is needed and relaxes when more air is needed.

Finally, the air is carried by the bronchioles into the alveolar clusters/bundles. Alveoli (alveoli) are very small bubbles with extremely/very thin walls. Each of these bubbles is called an alveolus. A cluster of alveoli around a bronchiole, like a bunch of grapes around a stalk. Thus all the alveoli in the alveolar cluster are connected to a single bronchiole. The alveoli are where the blood releases CO2 and takes in oxygen. Your lungs are tightly packed with them.

In fact, each lung contains about 150 million alveoli. Despite all the tissue your lungs contain, your lungs are still very light, like a sponge.

The wall of each alveolus is composed of bands of elastin. We recall that elastin is also found in the skin. Elastin allows the skin as well as the wall of each alveolus to stretch when you inhale and return to its normal size when you exhale.

Emphysema (medical english)
People often get emphysema as a result of smoking. Smoking destroys the elastin fibers in the alveoli, making it impossible for the alveoli to return to its normal size after it is stretched. If the alveoli are still stretched, it can be difficult to exhale (push air out of the lungs). People with emphysema can use up to a quarter of their energy just to breathe.

(Medical English) Translator: Minh Man Huynh