Why blood is red?

Because it contains red blood cells!

Why blood is red? They are tiny sacs, filled with a liquid colored red, called hemoglobin. It is hemoglobin that captures the oxygen from the air you have just breathed into your lungs. It is she who carries it in your body, inside the blood vessels.

Once in your muscles or in your brain, hemoglobin releases oxygen. It is replaced by carbon dioxide, which the hemoglobin will now carry into your lungs. There, this poisonous gas is released into the air you breathe.

Mixed reds and whites

During a blood test, if the blood collected in a test tube is allowed to stand, a curious phenomenon is observed. Particles fall to the bottom. These are the billions of red blood cells in your blood. Among these particles, there are also white blood cells: they help your body to defend itself against germs. And above these particles, there remains a yellow liquid: plasma. Blood is a mixture of blood cells and plasma.

Why blood is red?

The blood is red and there is indeed a rational explanation in this story, and why not a simple physicochemical explanation.

It is the blood that diffuses oxygen to every part of the body and eliminates poisons and waste. Pumped by the heart, oxygenated by the lungs, and then distributed by the arteries and blood vessels, it is made up of plasma in which many cells are bathed. The three best known are red blood cells (or red blood cells, which fix and distribute oxygen), white blood cells (or leukocytes, responsible for eliminating infectious agents), and platelets (or thrombocytes, which ensure coagulation).

With the sole exception of horseshoe crab (a marine arthropod with blue blood due to the replacement of hemoglobin by hemocyanin), all animals have red blood. Is there anything in the blood that stains it this way?

Red blood cells: responsible but not guilty

Usually, we imagine that the blood is red because it contains red blood cells. But this is not an answer because it does not explain anything, on the contrary, it amounts to asking why red blood cells are red. They are the ones that carry oxygen from the lungs to the muscles and get rid of their waste, the main one being carbon dioxide. They are, in part, made up of hemoglobin which is a red pigment that fixes oxygen.

Hemoglobin contains iron. This element, when subjected to white light, returns only photons whose wavelength is red. In addition, in hemoglobin molecules, iron associated with oxygen creates oxyhemoglobin, which gives blood its red color.

The red color of the blood, therefore, results from the oxidation of the iron elements contained in hemoglobin. Blood is, schematically, red for the same reasons rust is reddish-orange in color, namely oxidation.

Another question haunts you, the blood is red but if you take a good look at your veins, you only see blue. In fact, your skin acts as a filter, letting only the blue pass through.

Do you know why the blood is red?

Unlike our Vulcan friends, we humans do not have green blood, but rather red blood. Why?

Let’s start at the beginning: what is blood again?

Blood is life!

In the body of an adult, a man circulates between 5 to 6 liters of blood and 4 to 5 liters in a woman. The blood circulates in a complex network of blood vessels, the length of which is more than 100,000 km, or 7 times the diameter of the earth!

Every day 100,000 heartbeats will propel and move the circulating blood. It is in fact the blood, or blood plasma, that allows each part of our body to receive oxygen and eliminate wastes, such as carbon dioxide.

A very large number of cells are bathed in the plasma. The three main ones are:

• The red blood cells that distribute oxygen
• The white blood cells that remove infectious agents
• The pads that ensure coagulation.

All Terrans have red blood with the exception of the Limulus, a marine animal, which has blue blood!

So what is responsible for this red coloration in our blood?

The culprit is hemoglobin.

But what is hemoglobin?

It is a protein, which is found in red blood cells. It contains iron and is able to fix oxygen.

In hemoglobin molecules, iron combined with oxygen creates oxyhemoglobin, which gives blood its red color.

The red color of the blood, therefore, results from the oxidation of the iron elements contained in hemoglobin.

So why when I look at my veins I don’t see red but blue?

Because our skin acts as a filter and only lets us see the color blue!