The giraffe has a complex cardiovascular system, and is unique amongst mammals in having a head that may be up to 3m
above its heart. In order to provide its head with sufficient nutrients and oxygen, the giraffe's heart must therefore pump hard enough
to overcome the huge hydrostatic pressure generated by the tall column of blood in its neck. This results in the giraffe having extremely
high blood pressure (280/180 mm Hg) and a heartbeat of up to 170 beats per minute. Research has revealed that arterial pressure near
the giraffe heart is about twice that in humans, to provide more normal blood supply to the brain. Thanks to their huge lungs which can
hold 55 litres of air, they are also able to put plenty of oxygen into their blood.
It was previously thought that a giraffe had a really big heart, but recent research has revealed that there isn’t room in the body cavity for this. Instead, the giraffe has a relatively small heart and its power comes from a very strong beat as a result of the incredibly thick walls of the left ventricle.
To protect the giraffe's brain from sudden changes in blood pressure when it lowers its head to drink, it has valves to stop the back-flow of blood and elastic-walled vessels that dilate and constrict to manage flow.