In the lungs, what type of blood vessels surround the alveoli to allow rapid gas exchange?

• A. Venules
• B. Elastic arteries
• C. Capillaries
• D. Arterioles

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the function of alveoli in the lungs. Alveoli are tiny air sacs where gas exchange occurs between the air and the blood.
2. Step 2: Recall that for efficient gas exchange, blood vessels must be very thin-walled and closely associated with alveoli to allow oxygen and carbon dioxide to diffuse easily.
3. Step 3: Identify the types of blood vessels listed: venules, elastic arteries, capillaries, and arterioles, and consider their structure and function.
4. Step 4: Recognize that capillaries are the smallest blood vessels with thin walls, making them ideal for gas exchange as they form a dense network around alveoli.
5. Step 5: Conclude that capillaries surround the alveoli to facilitate rapid diffusion of gases between the air in the alveoli and the blood.