Question

In alveoli of the lungs, the air at the site of gas
exchange, is separated from the blood by
(a) alveolar epithelium only
(b) alveolar epithelium and capillary endothelium
(c) alveolar epithelium, capillary endothelium and
tunica adventitia
(d) alveolar epithelium, capillary endothelium, a
thin layer of tunica media and tunica adventitia

Answer 1

Answer:

In alveoli of the lungs, the air at the site of gas  exchange, is separated from the blood by Option B: alveolar epithelium and capillary endothelium

Explanation:

Alveoli are small air sacs present in our lungs. They consume the oxygen that helps our body to keep going. there are around 48 million alveoli  at the end of the 'bronchial tubes'. When we inhale, alveoli expands to take in oxygen and when we exhale, carbon-di-oxide moves out and alveoli shrinks.

The process of exchange of these two gases: oxygen and carbon-di-oxide is called gas exchange. These two are separated from the blood by 'alveolar epithelium' and 'capillary endothelium'. Thus, the correct answer is Option B,  'Alveolar epithelium and capillary endothelium.'