– The blood is red because of the hemoglobin, a protein that is responsible for carrying oxygen in the red blood cells
The blood is never blue, but it has some red tint. However, the veins through which passes the red blood act bluish because of the way the tissue and the blood reflect light.
The blue color of the veins is a consequence of the way the light is reflected.
LIGHT Is “Guilty” For Everything
When light would become due in human tissue, it is reflected in all directions through the cells and other structures. This light is either absorbed in the tissue or fading across the skin surface. The light that disappears across the surface of the skin, or reflects, we can see with the naked eye.
Blood is red because of the hemoglobin, a protein that is responsible for carrying oxygen in red blood cells, which absorbs blue light and very much reflects red light. Just remember when someone suddenly gets a blue face, which usually means that the body does not have enough oxygen.
Veins unlike arteries carry reduced blood, which in the tissue around the veins absorbs more red light than oxygenated blood (in the arteries).
The more we absorb red light, the less we see. When the red light is absorbed in the veins, it also reflects from the tissue around them, so on the surface of the skin we see that the part above the veins is red rather than around them.
VEINS ACT BLUE BECAUSE THEY CARRY REDUCED BLOOD
The deep veins act blue because they contain reduced blood, which reflects fewer red lights than other tissues.
This creates sort of optical illusion. The vein looks blue, not because it reflects more blue light, but because less red light is reflected off of the vein, rather than tissue around it.
As waves of blue light are shorter than the red, veins deeper below the surface of the skin, look bluer.
This seems contradictory, but it means that it will absorb the long, red light, and that the blue light will highlight over veins and “bounce” back in our eyes before it can be absorbed.
Briefly, veins act blue because they carry reduced blood, which means less red light is reflected from the surrounding tissues. As deeper the vein is the bluer it seems.