Question

Which of the following statement(s) is (are) true for respiration?

• A. During inhalation, ribs move inward diaphragm is raised.
• B. In the alveoli, exchange of gases takes place i.e.oxygen from the alveolar air diffuses into blood and carbon dioxide from blood to the alveolar air.
• C. Alveoli increases surface area for exchange of gases.
• D. Both B and C.

Answer 1

The correct option is D Both B and C.

The main respiratory surface in humans is the alveoli, which are small air sacs branching off from the bronchioles in the lungs. They are one cell thick and provide a moist and extremely large surface area for gas exchange to occur. Capillaries carrying deoxygenated blood from the pulmonary artery run across the alveoli. Due to the enormous number of alveoli (approximately 300 million in each human lung), the surface area of the lung is very large (75 m2). Having such a large surface area increases the amount of gas that can diffuse into and out of the lungs.