Question

Why are arteries red and veins blue?

Answer 1

Human blood is red because haemoglobin, which transports oxygen and is transported in the blood, is iron-rich and red in colour. Blue blood is found in octopuses and horseshoe crabs. This is due to the fact that hemocyanin, the protein that transports oxygen in their blood, is blue.

Complete answer:
Because of the differential in oxygen dissolved, the blood that travels through them is brighter red in arteries and a deeper maroon in veins. Because arteries are often found at deeper depths, veins are the only blood vessels visible at the skin's surface. Because of the differing absorptions of red and blue wavelengths, light impacting on skin tends to portray veins as bluish. This does not accurately portray the colour of the vessels.

Because of the colour of oxy-haemoglobin in the erythrocytes, arterial blood is a brighter red within the arteries. Because the oxygen in the veins has been depleted, the blood has turned a darker crimson, almost maroon colour.

The blood vessels that carry blood to the body are known as arteries (shown in red). The blood channels that return blood to the heart are called veins (blue).

The change in shape of the red blood cell when oxygen links to haemoglobin in the blood cell (oxygenated) versus does not bind to it (deoxygenated) causes deoxygenated blood to be darker (deoxygenated). The colour of human blood is never blue.

Blue light has a shorter wavelength (about 475 nanometres) and is more easily scattered or deflected than red light. Because it is quickly dispersed, it merely penetrates a fraction of a millimetre into the skin. In comparison to the rest of your skin, your veins will seem blue.

Because haemoglobin coupled to oxygen absorbs blue-green light, it reflects red-orange light into our eyes, making them look red. When oxygen attaches to iron in the blood, it turns brilliant cherry red. Blood is a darker crimson colour when it is not coupled to oxygen. Veins' bluish appearance is merely an optical illusion.

Note:-
When blood returns to the heart, it is pumped to the lungs by the heart. Carbon dioxide is drawn from the blood and breathed back into the atmosphere through the lungs. Each fresh breath brings oxygen into the lungs, restoring blood before it is pumped back out to the body's cells. The procedure then begins all over again. How long will the entire procedure take? It didn't take long at all! In less than 60 seconds, your heart can pump blood to all of your body's cells.