Question

How are lungs designed in human beings to maximize the area of exchange of gases?
A. Presence of a huge number of alveoli
B. Presence of a huge number of alveoli which possess a network of capillaries over their surface
C. Presence of a huge number of alveoli which possesses a network of capillaries over their surface, functioning as a respiratory surface
D. None of these

Answer 1

Hint: Lungs are respiratory organs in human beings. They are the site of gaseous exchange in the body. Carbon dioxide collected from cells as their waste product is collected by blood vessels and is diffused out of the body through the lungs. Fresh air containing oxygen is respired through the lungs. The oxygen diffuses through a network of capillaries.

Complete answer: The lungs are the major organs in the human body that maintain the key life process of breathing and respiration. These are sites of the body’s gaseous exchange. The lungs are present near the backbone on both sides of the heart. The lungs are composed of various structures that help in gaseous exchange. The first part of the lungs is a narrow apex that extends to the rot of the neck. The trachea is a long cylindrical cartilage structure that is attached to the lungs centrally. The trachea divides into two main branches that are termed primary bronchi. Primary bronchi are wide tubules that further divide to form narrow tubules called secondary bronchi. The secondary bronchi make tertiary bronchi and finally, these tertiary bronchi divide into bronchioles that are very fine and thin tubules connected to lobular structures at their ends. These globular structures are sacs that are called alveoli.

The alveoli have very thin walls, beneath which lie capillaries. Capillaries are a fine network of thin blood vessels. The alveoli as well as the capillaries are arranged in a coiled manner. Due to this, they provide maximum area for gaseous exchange. Also, diffusion of gases takes place through both of these structures.
Thus, the presence of a huge number of alveoli which possess a network of capillaries over their surface, functioning as respiratory surface contributes to providing a maximum area for gaseous exchange.
So, the correct answer is option option C.

Note: The alveolar sacs are very sensitive structures and are easily targeted by various virus and bacterial species. For example, in the case of coronavirus disease, the virus attacks the alveoli of the lungs. This leads to the accumulation of mucus in these sacs. The fluid blocks efficient air exchange. This leads to difficulty in breathing.