Welcome to brain stuff from how stuff works. Hey, brain stuff, it's Christian saga. Do you remember in the movie Carry where they dumped pig blood on that girl at her prom? Well? The Annals of Human Biology actually published an article in two thousand twelve showing that humans are excellent detectors of pig blood, but we are far less developed at detecting human blood. They concluded that human blood has no specific
smell or appearance that triggers immediate recognition. So blood is always red, right, But why does it have to be read? Contrary to popular belief, it's not blue when it's in our bodies, even when it's deoxygenated. But oxygen is part of the color, along with the protein molecule hemoglobin that attaches to oxygen. It carries from the lungs two muscles as blood gets pumped through the human body. And while blood is always red, its shade depends on how much
oxygen it's carrying. For instance, when you cut a person's arteries open, they bleed this really bright red blood because of the complex formed between hemoglobin, iron and lots of oxygen. But if you look deeper into the circulatory system and peered into a vein that was delivering all of its oxygen, you would see that the blood is a deeper maroon color, So veins they look blue or green mainly because of
skin and skin pigmentation plays a big role. Since everyone's skin is a different color, our veins look different, especially because the tissue above our veins scatters red light, but let's blue light right on through. Even though veins are a reddish brown, they appear to be blue from the outside. So is the way human beings perceive color and other factor here as well. Yes, researchers have shown that it
is partially an optical illusion. So light colored skin reflects most light and blood absorbs most light, particularly dark deoxygenated blood. It reflects a little blue and some red, But since the skin surrounding the veins scatters and reflects a lot of red light, the veins look way bluer in comparison. The ratio is so skewed that it tricks the eye. In fact, some animals actually bleed other colors, like slugs
and molluscs, they bleed blue. Check out the brain stuff channel on YouTube, and for more on this and thousands of other topics, visit how stuff works dot com,