Philadelphia Fire Department Practice Exam

What is the primary function of alveoli in the human respiratory system?

1. Transferring carbon dioxide from blood to air

2. Transferring oxygen from air to the blood

3. Filtering toxins from inhaled air

4. Regulating air pressure in the lungs

The correct answer is: Transferring oxygen from air to the blood

The primary function of alveoli in the human respiratory system is the transfer of oxygen from the air to the blood. Alveoli are tiny air sacs located within the lungs that provide a vast surface area where gas exchange occurs. This process is essential for respiration, as oxygen is transferred from the inhaled air into the blood, where it binds to hemoglobin in red blood cells and is then transported throughout the body to nourish tissues and organs. The structure of alveoli is specifically designed to maximize this gas exchange process. They are very thin-walled, which allows for efficient diffusion of oxygen into the bloodstream. Additionally, they are surrounded by a network of capillaries that carry deoxygenated blood from the body, ensuring that oxygen can enter the bloodstream quickly and effectively. While the other functions mentioned in the choices can play a role in respiration or lung health, such as the removal of carbon dioxide or filtering the air we breathe, they are not the primary function of alveoli. The focus on the alveoli's role in oxygen transfer highlights their critical importance in maintaining the body's overall oxygen supply and supporting cellular metabolism.