Certified Hyperbaric Technologist Practice Test

How do oxygen molecules enter the blood from the air we breathe?

1. Through the stomach

2. Through the lungs

3. Through the skin

4. Through the liver

The correct answer is: Through the lungs

Oxygen molecules enter the blood primarily through the lungs. When we breathe in air, it travels down the trachea and into the bronchi, which branch into smaller bronchioles that lead to the alveoli, tiny air sacs in the lungs. It is in the alveoli where the exchange of gases occurs. In this process, oxygen diffuses across the thin walls of the alveoli and into the surrounding capillaries, which are tiny blood vessels. Once in the capillaries, oxygen binds to hemoglobin molecules in red blood cells, facilitating its transport throughout the body. This process is essential for supplying oxygen to tissues and organs, which is crucial for cellular respiration and energy production. The other options, such as entry through the stomach, skin, or liver, do not play a role in the respiratory process of oxygen uptake. The stomach is involved in digestion, the skin has a minimal role in gas exchange, and the liver primarily functions in metabolism rather than gas exchange.