Questions: The Respiratory System

Question 1

What is the main function of the alveoli in the lungs?

• A. To filter dust from the air
• B. To warm the air before it enters the blood
• C. To exchange oxygen and carbon dioxide between air and blood
• D. To produce mucus that traps bacteria

Answer: (C)

Alveoli are tiny air sacs at the ends of the smallest airways in the lungs. Their thin walls allow oxygen to pass from the air into the blood, and carbon dioxide to pass from the blood into the air. This gas exchange is the core function of the respiratory system.

Question 2

The lungs actively pump air in and out of the body like the heart pumps blood.

• T. True
• F. False

Answer: False

The lungs themselves do not have muscles that pump. Instead, the diaphragm (a muscle below the lungs) and the muscles between the ribs contract to expand the chest cavity, which pulls air in. When these muscles relax, the chest cavity shrinks and air is pushed out. The lungs are passive — they expand and contract because of the muscles around them.

Question 3

Explain why your body needs to breathe continuously and cannot simply store a large supply of oxygen.

Model answer: Every cell in the body is constantly using oxygen to convert food into energy (cellular respiration) and producing carbon dioxide as waste. The body cannot store much oxygen, so breathing must happen continuously to keep supplying oxygen and removing carbon dioxide. If oxygen delivery stops, cells begin to die within minutes.

This connects the respiratory system to cellular respiration and explains the urgency of breathing. Unlike food or water (which the body can store for days), oxygen must be continuously resupplied because cells use it as fast as it arrives.