Blood in the human body is always red, though it can vary in shade from a bright cherry red to a darker brick red depending on the oxygen content. The red color is due to the presence of hemoglobin, a complex protein molecule found in red blood cells.
When blood is oxygenated, it's a brighter red because the hemoglobin binds to oxygen. As blood circulates throughout the body, it loses oxygen, resulting in a darker shade of red. This is why veins, which carry deoxygenated blood back to the heart, appear bluer than arteries, which carry oxygenated blood away from the heart.
However, the blue color we see in veins is an illusion caused by the way light interacts with the skin. The skin absorbs some colors of light better than others, and the blue wavelengths tend to be absorbed less, making the veins appear blue.
Here are some key points to remember about blood color:
- Blood is always red, even when deoxygenated.
- The appearance of blue veins is an optical illusion.
- The color of blood varies depending on the oxygen content, with oxygenated blood being brighter red and deoxygenated blood being darker red.
