What makes blood blue? Do we really have blue blood circulating in our bodies?
The iron in red blood cells circulating through the veins is not bound to oxygen. Oxygen was given off in the capillaries. The unbound iron turns a darker red. We don’t actually have blue blood in our veins. The reason our blood looks blue is because of how light passes through our skin to those veins and hits those dark red blood cells. Light refraction makes the veins and the blood within them look blue. So, it is basically a complicated physics thing dealing with light refraction. OKIM IM is right… arthropods such as the horseshoe crab really do have blue blood.
