Gas Exchange in the Respiratory System

The human respiratory system is responsible for the exchange of gases between the body and the environment. This system ensures that oxygen is brought into the body for vital cellular processes while also expelling carbon dioxide, a waste product of metabolism. When you inhale, air enters through the nose or mouth, travels down the trachea, and into the lungs. Within the lungs, oxygen moves into the blood, and carbon dioxide moves from the blood into the lungs to be exhaled.

Which structure in the respiratory system is primarily responsible for the exchange of gases between the air and the bloodstream?