What happens to the blood when it
is taken to the lungs? (A) It releases glucose. (B) It absorbs glucose. (C) It becomes oxygenated. Or (D) it becomes deoxygenated.
The blood that’s traveling from the
heart to the lungs is deoxygenated. This means it contains very little
oxygen because the oxygen has already been delivered to the tissues which need it
for cellular respiration.
Let’s zoom in on a small section of
the lung to see what happens to the blood when it arrives. You may recall that the lungs
contain structures called alveoli, or singular alveolus, which are the site of a
process known as gas exchange. There are millions of alveoli in
the lungs, and you can think of them as being like balloons, which inflate and
deflate when we breathe air in and out.
You can see in this diagram that
each alveolus is surrounded by a blood capillary. As we’ve already said, the blood
arriving at the lungs is deoxygenated. Deoxygenated red blood cells are
often represented in blue, as we can see here. But it’s important to remember that
in reality they are always red.
Because the air that is breathed
into the alveolus contains a much higher concentration of oxygen than the
deoxygenated red blood cells, oxygen diffuses from the alveolus into the capillary
as the blood moves through it. The oxygen is then picked up by the
red blood cells, so they become oxygenated. This oxygenated blood then returns
to the heart so it can be pumped all around the body.
We have therefore determined that
the correct answer is (C). When the blood is taken to the
lungs, it becomes oxygenated.