IFPA Trainer Practice Exam

The lungs exchange CO2 for O2 at the tiny air sacs known as ______.

1. Alveoli

2. Larynx

3. Trachea

4. Pharynx

The correct answer is: Alveoli

The lungs exchange carbon dioxide (CO2) for oxygen (O2) at the alveoli, which are tiny air sacs located at the end of the respiratory tree. The primary function of the alveoli is to facilitate gas exchange; their thin walls allow oxygen from inhaled air to pass into the blood, while simultaneously allowing carbon dioxide from the blood to diffuse into the air sacs to be exhaled. Each alveolus is surrounded by a network of capillaries, which is where the blood picks up oxygen and releases carbon dioxide. This process is crucial for maintaining the body’s oxygen supply and removing metabolic waste. The large surface area provided by the numerous alveoli in the lungs maximizes the efficiency of this gas exchange. The other terms listed refer to different parts of the respiratory system. The larynx is involved in sound production and protecting the airway during swallowing. The trachea serves as the windpipe connecting the larynx to the bronchi, directing air into the lungs. The pharynx is a muscular tube that serves both respiratory and digestive systems but is not involved in the gas exchange process. Thus, it is the alveoli that are integral to the gas exchange function in the lungs.