Question

In the lungs, air passes through a large number of small tubes called ______ and then reaches the tiny air-sacs called __________

• A. bronchioles
• B. alveoli

Answer 1

Lungs:

1. Lungs are the chief respiratory organs where the exchange of gases takes place.
2. It is a pair of spongy, elastic organs that lies in the thoracic cavity.
3. The respiratory system in humans includes the nose, pharynx, larynx, trachea, bronchi and the lungs.
4. The air enters our body through the nostrils and then goes into the nasal chamber. From there, it travels into the pharynx and then to the larynx.
5. The larynx is followed by a long tubular structure known as the trachea or windpipe.
6. The trachea, also known as the windpipe posteriorly divides into two main structures known as primary bronchi and secondary bronchi.
7. These bronchi split into numerous branches known as bronchioles.
8. The bronchioles by repeated division transform into finer branch tubes known as alveolar tubes. The terminal ends of these tubes bulge out to form extremely thin-walled tiny air pockets known as alveoli.
9. Finally, a large number of terminal bronchioles in turn together form a spongy structure known as the lung.

Final answer:
In the lungs, air passes through a large number of small tubes called bronchioles and then reaches the tiny air sacs called alveoli.