Question

Number of alveoli in the two human lungs is?
A. 600 – 800 million
B. 200 – 300 million
C. 1 – 2 million
D. 100,000 – 150,000

Answer 1

Hint: Alveoli are important units of the respiratory system. They are tiny balloon-like sacs present inside the lungs. The number of alveoli in the lungs is indicative of the total lung capacity. Although the number varies as per lung size, a common range is set for the average number of alveoli in humans.

Complete answer:
There are approximately 600 – 800 million alveoli in the two lungs of a human being.
The alveoli are sac-like structures that store the air that one breathes in. The alveoli are stretchable. When a person breathes in, they expand. When a person breathes out, the alveoli shrink back.
The major functions of the alveoli are:
> Ventilation
> Diffusion
> Perfusion
The alveoli pick up the oxygen from the inhaled air and release the carbon dioxide along with the exhaled air. The alveoli are associated with a network of capillaries that take up the oxygen and transport it to various parts of the body through the circulatory system. Similarly, the capillaries carry the carbon dioxide to the alveoli for exhalation.
A large number of alveoli increase the surface area for the gaseous exchange. The average capacity of our lungs is 1.3 to 2.1 gallons of air per minute. The alveoli are able to transport 0.3 litres of oxygen to the blood in a minute.

The correct answer is – A. 600 – 800 million.

Note:
Each lung consists of a structure known as bronchi. The bronchi branches into smaller fragments known as bronchioles. An alveolar duct is present at the end of each bronchiole. The alveolar duct is the part that connects to numerous alveoli at once. Alveoli are present in bundles and are referred to as alveolar sacs.