Final answer:
Gas exchange in the respiratory system takes place in the alveoli, which are in direct contact with capillaries of the circulatory system. Due to their large surface area and thin-walled structure, oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood to the alveoli to be exhaled.
Step-by-step explanation:
The process of gas exchange between the air and circulating blood takes place in the alveoli. Alveoli, which are thin-walled and resemble tiny bubbles, are found at the end of the bronchioles attached to alveolar ducts and are in direct contact with capillaries of the circulatory system. The interplay of structure and function in the respiratory and circulatory systems ensures that oxygen will diffuse from the alveoli into the blood and carbon dioxide will diffuse from the blood into the alveoli to be exhaled.
This gaseous exchange occurs due to the large surface area (about 100 m², approximately half a tennis court) provided by the alveoli, combined with their thin-walled structure. The entire process starts with the inhalation of air which travels down the pharynx, through the trachea, bronchi and bronchioles to finally reach the alveoli, which is the site of gas exchange.
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