Why are Blood Transfusions So Tricky?
How blood differs from person to person — and person to animal
Blood, that icky red liquid we all prefer to keep mostly inside our bodies, is not unique to humans. All mammals, reptiles, birds, fish, and amphibians have iron-rich red blood flowing through their veins and arteries.
But human blood isn’t the same as, say, pig blood. They both look the same to the naked eye, but they aren’t interchangeable. We cannot use animal blood for a transfusion in surgery. And we can only receive transfusions from people with the same blood type as us.
Why? What makes different types of blood, well, different? And how can we tell the origin of a sample of blood?
Blood is actually really complex
Blood looks like a uniform red goo. Despite the myth, human blood is never blue. It can look blue in our veins — thanks to our skin absorbing more red light than blue light — and veins are often colored blue in drawings in anatomy textbooks to distinguish them from arteries. But whether in our bodies or out, blood is red.
And when viewed through a microscope, blood is a complex blend of many different types of cells.
