GENERAL HISTOLOGY

Detailed explanation-1: -Alveoli represent the major sites of gas exchange. Their presence increases the surface area of the lung to maximize gas exchange, much like villi and microvilli increase the absorptive surface area of the digestive tract.

Detailed explanation-2: -The small round alveoli allow for an amazingly large surface area for this gas exchange to take place. Remember, the blood capillaries must be in contact with the respiratory surface for gas exchange to take place. Therefore, the greater the surface area, the more gas exchange can occur.

Detailed explanation-3: -Alveoli in lungs improve gas exchange by increasing the surface area of the lungs.

Detailed explanation-4: -Complete answer: The moisture layer in the alveoli allows gases to dissolve so that they can easily diffuse. The alveoli, supported by the thick network of capillaries covering them, have a very wide overall surface area and a very strong blood supply.

Detailed explanation-5: -(b) In the alveoli, exchange of gases takes place, i.e., oxygen from alveolar air diffuses into blood and carbon dioxide from the blood into the alveolar air. (c) Haemoglobin has a greater affinity for oxygen than carbon dioxide. (d) Alveoli increases the surface area for the exchange of gases.