Giraffes are fascinating animals. They have the same number of vertebrae in their necks as humans do—seven—but each one is nearly a foot long.

They have long, purple tongues too—nearly two feet—that can grasp things as easily as a monkey’s tail can, which they use to pull leaves and fruits from high branches.

All four giraffe species are covered in spots. And each individual’s spots are as unique as a fingerprint.

But the most fascinating thing about giraffes...is their cardiovascular system.

Their head is so high up that to deliver normal blood pressure to their brain they must generate twice normal pressure at their heart. Enough blood pressure to kill a person.

They do that with a heart that’s two feet long and weighs up to 25 pounds.

They also have specialized one-way arteries. When a giraffe tilts its neck down, valves in its jugular close, storing up to a liter of blood, to keep it from flooding the brain.

When the giraffe lifts it head back up, the blood rushes out of the jugular back to the heart, pressurizing it so it can pump blood all the way back up the neck to the brain.

Arteries in the legs constrict to stop blood from pooling in the feet, and special connective tissue acts as natural compression socks.

The giraffe’s miraculous blood pressure control system is still not well understood by scientists. But they’re studying it to see if it might one day help humans manage our own high blood pressure.