JAMB - Biology (2004 - No. 17)
The surface of an alveolus in a mammal is well supplied with tiny blood vessels known as
arterioles
venules
arteries
capillaries
설명
The tiny blood vessels found on the surface of the alveolus are called capillaries. Capillaries are so small that red blood cells can only pass through them one at a time.
How capillaries work
- Capillaries are part of a network of arteries and veins that move blood throughout the body.
- The pulmonary artery branches off to deliver blood to the capillaries that surround the alveoli.
- The blood in the capillaries is low in oxygen and high in carbon dioxide.
- Oxygen moves from the air in the alveoli into the blood in the capillaries.
- Carbon dioxide moves from the blood in the capillaries into the air in the alveoli.