Why is our blood red and not blue?

Human blood is always red, whether it’s in a vein or from a wound. But why do we see veins (veins) blue when we look through the skin?

What are blood cells?

Human blood is not only a liquid, but it also contains a lot of things for your body to function. Most of our blood is made up of plasma, where blood cells are suspended within. Anything the blood carries (other than oxygen) is dissolved in the plasma. “The most common type of blood cells suspended in plasma are red blood cells,” says Dr. David Gatz of Mercy Medical Center in Baltimore, USA.

Human blood is red because it contains red blood cells and hemoglobin . This is a protein that contains a red compound called heme , which is important in transporting oxygen in the blood stream throughout the body. Heme contains an iron atom bound to oxygen, and it is this molecule that transports oxygen from your lungs to other parts of your body.

Our eyes perceive particular colors of chemicals based on the wavelengths of light they reflect. Because hemoglobin bound to oxygen absorbs blue light, it reflects red-orange light into our eyes, causing the color to appear red. That’s why blood turns bright red when oxygen binds to iron, if oxygen is not present, blood will be darker red.

Oxygen causes red blood cells to appear red. If your oxygen levels are low because you have trouble breathing, all the blood in your body may be darker.

Many people try to stop bleeding at home, but if your cut or wound is spewing bright red blood, it means you’ve injured an artery, not a vein, and needs urgent medical attention.

Carbon monoxide – a potentially deadly gas – can also bind to heme, with a bond 200 times stronger than oxygen. In the presence of carbon monoxide, oxygen cannot bind to hemoglobin, resulting in death. Because carbon monoxide adheres to the heme so tightly, the blood remains bright red, sometimes causing a pink appearance on the cheeks of victims of carbon monoxide poisoning.

Why is our blood red and not blue?
Human blood is always red because of hemoglobin. (Photo: Hello Bacsi).

Sometimes when we look through the skin we see the blood is blue. You may have heard that the blood in our veins is blue because when it returns to the lungs, it lacks oxygen. But this is not correct, human blood is never blue . The blue color in the veins is just an optical illusion. Blue light does not penetrate as deeply into tissues as red light. If the blood vessels are deep enough, your eyes will see more reflected blue light than red light, which is because the blood absorbs part of the red wavelength.

But blue blood exists in the animal world . It is common in species such as squid and horseshoe crabs. Their blood contains a chemical called hemocyanin , which contains copper atoms to carry oxygen. Some other animals even have green or purple blood. The reason for this difference is that these blood types carry a different oxygen-carrying molecule than our hemoglobin.

Why is our blood red and not blue?
The blue blood of horseshoe crabs is an important raw material in the pharmaceutical industry. (AP photo/Steve Helber).

Apart from these exceptions, most animals’ blood is red. But this red is not the same color as the blood flowing in the veins of man. In different species, the variations of hemoglobin also differ. This allows scientists to distinguish blood samples from different animals.

If you look closely, you can see, when it bleeds, over time the blood will start to turn dark red, and when the blood dries it gets even darker, and then its hemoglobin will break down into a compound. substance called methemoglobin . Over time, the dried blood continues to change, becoming increasingly darker due to another compound called hemichrome . This constant change in color and chemistry allows forensic scientists to determine when blood was present at crime scenes.