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The structure labeled A is alveoli and the delicate surrounding is B brochures, C diaphragm, D bronchi.
Alveoli are the important part of the respiratory system. Its function is to exchange carbon dioxide and oxygen molecules from and into the bloodstream. They are the end point of the respiratory system and it starts when we inhale air into the nose or mouth.
Rich air which is oxygen travels down the trachea and to the smaller passage which is called bronchioles and passes through the alveolar duct then finally to the alveolus.

The diagram shows the respiratory structure of humans and their structures. Label A in the diagram is alveoli surrounded by B. bronchioles, C. diaphragm, and D. bronchi,

What is the respiratory system?

A respiratory system is an organ system that enables the inhalation and exhalation of the gases. Many parts like bronchi, bronchioles, ribs, diaphragm, alveoli and sacs make the respiratory system.

Alveoli are the essential part of the respiratory system that is the region of the exchange of carbon dioxide and oxygen gases. The network of the capillaries around it allows the exchange of gases from the bloodstream.

Therefore, the label A is the alveoli of the respiratory system.

Learn more about alveoli here:

https://brainly.com/question/9911030

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