In the lungs, which type of blood vessel forms a dense network around the alveoli to allow gas exchange?

• A. Arterioles
• B. Capillaries
• C. Arteries
• D. Veins

Answer: (B)

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: Recognize that for efficient gas exchange, blood vessels must be very close to the alveoli to allow oxygen and carbon dioxide to diffuse easily.
3. Step 3: Identify the type of blood vessel that forms a dense network around the alveoli. These vessels are very thin-walled to facilitate gas exchange.
4. Step 4: Recall that capillaries are the smallest blood vessels with thin walls, allowing oxygen to pass from the alveoli into the blood and carbon dioxide to pass from the blood into the alveoli.
5. Step 5: Conclude that the blood vessels forming the dense network around alveoli for gas exchange are capillaries, not arterioles, arteries, or veins.