Stand up too fast and you get dizzy. A giraffe drops its head 6 feet to drink - and stays perfectly fine. How? Inside that neck is one of the most extreme cardiovascular systems on Earth: a ~25-pound heart pumping blood straight up against gravity at around 280/180 - more than double a human's. So why doesn't all that pressure knock it out when it bends down to drink? The answer is a hidden mesh of vessels at the base of the skull called the rete mirabile - the "wonderful net" - plus one-way neck valves and legs wrapped in skin so tight it works like a built-in compression stocking. A giraffe survives a blood pressure that kills millions of people every year - and never feels a thing. #giraffe #AnimalFacts #biology #anatomy #Science - @thenatureshock