The heart and lungs
are very closely connected. Not only do they fit closely together in
the chest, but they also work together to make sure that every part of
your body gets the oxygen it needs.
In our discussion of how the heart works, we said that blood is pumped
from the right side of your heart to your lungs. Just like the air you
inhale moves through passageways, the blood that flows through your
lungs moves through a set of branching pipes called pulmonary vessels.
The biggest pipes are called pulmonary arteries;
as the vessels move deeper into the lungs, they divide into smaller and
smaller branches, eventually becoming a large network of very
thin-walled vessels called capillaries. These vessels are important because they are the site of oxygen transfer from the alveoli,
across the alveolar and capillary walls, into the blood. If there is
trouble with the pulmonary vessels, you may have difficulty getting
oxygen into the blood.