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Question Video: Describing the Function of the Lungs in the Circulatory System Biology

What happens to the blood when it is taken to the lungs?

01:51

Video Transcript

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.

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