Question

How are alveoli designed to maximize the exchange of gases?

Answer 1

The alveoli in the lungs are designed as such to facilitate the maximum possible exchange of gases easily and efficiently.

Complete answer:
-Alveoli are moist, membranous, pouch-like air sacs that are made up of simple squamous epithelium. Alveoli are only one called thick and provide a large surface for the exchange of gases. An extensive network of blood vessels or capillaries is present in the wall of the alveoli.
When we breathe in, the air is sucked into the lungs and alveoli. The oxygen from the inhaled air diffuses into the blood and $CO_2$ from the blood brought from the body diffuses out into the air with the help of the capillary network.

Additional Information: -Alveoli consist of two different types of cells
-Type I pneumocytes- They are the cells that are responsible for the exchange of oxygen and carbon dioxide.
-Type II pneumocytes- They perform two important functions. They are responsible for the maintenance and repair of the damaged alveolar lining. Besides, they also secrete surfactant.
-The surfactants are phospholipids that help in maintaining the shape and surface tension of the alveoli. It also helps to prevent the collapse of alveoli during expiration. DPPC (Dipalmitoyl Phosphatidylcholine) is the main lipid component of the surfactant. It increases the compliance of the lungs.

Note: Diffusion of oxygen from the alveoli to capillaries occurs because the concentration of oxygen is lower in the capillaries. In the same manner, carbon dioxide diffuses from the capillaries to the alveoli because the concentration of carbon dioxide is lower in alveoli.