Multiple Choice
How thick are the walls of the alveoli and the capillaries involved in capillary exchange?
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19. The Blood Vessels
Capillaries
Multiple Choice
In the lungs, which type of blood vessel forms the dense network that surrounds (covers) the alveoli to allow rapid gas exchange?
A
Venules
B
Arterioles
C
Elastic arteries
D
Capillaries
Verified step by step guidance1
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.
Step 2: Recognize that for efficient gas exchange, blood vessels must be very thin-walled and form a dense network around the alveoli to maximize surface area contact.
Step 3: Identify the types of blood vessels: venules and arterioles are small vessels but do not form the dense network directly surrounding alveoli; elastic arteries are larger vessels that conduct blood away from the heart and are not involved in gas exchange.
Step 4: Recall that capillaries are the smallest blood vessels with thin walls, allowing oxygen and carbon dioxide to diffuse easily between the alveoli and the blood.
Step 5: Conclude that capillaries form the dense network covering the alveoli, enabling rapid gas exchange due to their thin walls and extensive surface area.
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