Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

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

1. To support the body and protect organs

2. To break down food for nutrient absorption

3. To facilitate gas exchange of oxygen and carbon dioxide

4. To produce hormones for regulatory functions

The correct answer is: To facilitate gas exchange of oxygen and carbon dioxide

The primary function of the alveoli in the respiratory system is to facilitate gas exchange of oxygen and carbon dioxide. Alveoli are tiny, balloon-like structures located at the end of the respiratory bronchioles in the lungs. They provide a large surface area and a thin barrier for the exchange of gases between the air inside the alveoli and the blood in the surrounding capillaries. When you inhale, oxygen from the air fills the alveoli, and it diffuses across the alveolar wall into the blood, where it binds to hemoglobin in red blood cells. At the same time, carbon dioxide—a waste product of cellular metabolism—diffuses from the blood into the alveoli to be expelled when you exhale. This process is vital for maintaining the body’s oxygen levels and removing carbon dioxide, ensuring proper cellular function. The other options pertain to functions not associated with the alveoli. Supporting the body and protecting organs involves the skeletal system, while breaking down food for nutrient absorption is a function of the digestive system. Producing hormones is a function of the endocrine system. Therefore, the role of the alveoli is distinctly related to gas exchange, making it the correct choice.