- The main role of the pulmonary circulation in the cardiovascular system is to facilitate the exchange of gases between the blood and alveolar air.
- This process is essential for oxygenating blood and removing carbon dioxide, which is a waste product of metabolism.

- In pulmonary circulation, deoxygenated blood is pumped from the right ventricle of the heart to the lungs via the pulmonary arteries.
- Within the lungs, blood flows through the pulmonary capillaries that surround the alveoli. Here, oxygen from the inhaled air diffuses into the blood, while carbon dioxide diffuses from the blood into the alveolar air to be exhaled.

- This gas exchange is critical because it ensures that systemic tissues receive oxygen-rich blood, which is necessary for cellular respiration and energy production.
- Unlike systemic circulation, the pulmonary circulation is not primarily responsible for delivering nutrients or regulating blood pressure systemically.

Therefore, the correct function of the pulmonary circulation aligns with Option 2: Exchange gases between the blood and alveolar air.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th Edition, Chapter 38: Pulmonary Circulation and Gas Exchange