【577期 英語時間】Is the blood in your veins coloured blue?
發佈時間：00:00 2021-06-17
Look at your body, and you will see that there are many thick or thin blue tubes near the surface of your skin. These are veins, which are channels for moving blood from all parts of the body towards the heart. People often claim that the blood in the veins is also blue in colour – but that is simply not true!
First, we have to understand why blood is usually red in colour. It is because of an organism called a red blood cell. These contain a kind of protein that helps carry oxygen. When the red blood cells are full of oxygen, which happens when they are in our arteries, our blood is bright red. However, the red blood cells in our veins contain little oxygen, so they have a different colour. But it is not blue at all; it is actually just dark red.
Why is it then that veins are blue in colour? Well, it is a bit like why the sky is blue. The veins are very near our skin. When we see the veins, what we actually see is the colour of the blood through the skin. Since the skin filters out most of the red light, what we see instead is the remaining blue light.
Another reason why we think the blood in veins is blue may be because most medical diagrams use the colour blue to indicate blood containing little oxygen, since it may be a bit confusing to use bright red for the oxygenfilled blood and dark red for the deoxygenated blood.
When we donate blood, it is taken from the veins, and this can be seen because the blood that comes out is just dark red, not blue!
Vocabulary
vein (n) 靜脈
red blood cell (n phr) 紅血球
protein (n) 蛋白質
artery (n) 動脈
filter (v) 過濾
deoxygenated (adj) 含氧量低的
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