Because of the distance the blood has to travel between the giraffe’s heart and its brain or the tip of its legs, the giraffe has developed a remarkably original circulatory system. Its enormous heart (almost 11 kg or 24 lbs.) beats twice as fast as that of a human (170 beats per minute at rest) and pumps more than 60 liters (15 gallons) of blood per minute to irrigate the enormous veins that run through the animal’s body.
But this power could be lethal when the animal lowers its neck and head. A bit like when you put your head down and feel the blood rush to your head. To prevent this from happening to giraffes, their veins are equipped with valves, a kind of sluice, which stop the blood flow when the animal puts its head down, but also when it lifts it up.
This ability to stop a large flow of blood was of great interest to NASA. Indeed, when pilots are subjected to high pressures generated by speed and altitude, their blood volume is drawn towards their limbs and their head is no longer irrigated. Using the giraffe’s circulatory system as a model, NASA was able to create an anti-gravity suit so that the blood of spacewalkers always reaches their brains.
(Source: especes-menacees.fr, Cécile Arnoud, Oct. 22, 2019)