Is Blood Blue or Red?

Blood can actually be both, depending on where in the circulatory system you're looking. The terms for when blood becomes blue or red, are deoxygenated or oxygenated, respectively, and you will see why blood can be both.

So let's take a look at the circulatory system and see when blood becomes deoxygenated (blue) and when it becomes oxygenated (red), shall we?

Picture of the human circulatory system
Courtesy from: Health, Medicine, And Anatomy Reference Pictures

The picture on the right shows how blood flows through the human body. This may seem a little daunting, but I will try to make it less complicated.

Blood works like a never-ending roller coaster. According to the National Space Biomedical Research Institute: 

·         Your deoxygenated blood flows through your heart and goes out through the pulmonary artery, which leads to the lungs so the blood can become oxygenated.

·         After being oxygenated, blood flows back into your heart and goes out the aorta, where it splits into arteries, and flows throughout your body.

·         After the oxygenated blood travels throughout your body, the blood will become deoxygenated and have to travel back into your heart, where the process will repeat itself continuously throughout your life.

So why will blood become blue, but also become red? If you have ever bitten your lip, or cut your finger and tried sucking on the blood, you've tasted a weird iron-like taste. That is because your blood contains iron.

When iron reacts with oxygen, blood becomes red. However, when the oxygen is used up, such as when it has gone throughout our entire body, the blood will become blue. It's kind of like when you try holding your breath for too long, and your face starts to turn a bluish color.

Deoxygenated and oxygenated blood seem similar because both are blood in our body, but they do work in different ways. When blood becomes deoxygenated, it flows through the veins, instead of the arteries, which is why when you look at your veins, it has a bluish color.

Furthermore, deoxygenated blood has to work much harder to get back to the heart than oxygenated blood. Blood that travels through the veins has to work against gravity to get back to the heart, unlike the blood in the arteries, were it works with gravity and has a much easier time getting to the outermost parts of your body.

Deoxygenated blood needs help to flow, so by moving your legs, hands, fingers, and toes, the blood in those parts of your body will move against gravity and make it back to the heart, where it will once again become oxygenated.

So why should we learn about blood? Blood is one of the main essences of life. We can donate our own blood to help save others, by way of blood transfusions. Sometimes, the only way to help save a person is with blood transfusions. Below is a video by the World Health Organization about blood donation. Click here to find out more about where and how you can donate blood.

By: World Health Organization

Have you donated blood before? What was it like?