Why do giraffes not have blood pressure problems?

Tall giraffes eating leaves from acacia trees.

Mr Giraffe is the tallest animal on earth!

His circulatory system is a marvel.


Because his heart pumps blood way up his long neck, and that takes a lot of pressure.

Yet, when he lowers his neck, the blood vessels in his brain and eyes do not burst.

“Why does the high pressure not rupture those delicate vessels or at least force leakage from them?” asked a scientific journal.

The answer appears to be due, in part, to a marvelous network of fine blood vessels appropriately called the “wonderful net.”

Blood from the neck arteries passes through this “wonderful net” before reaching the brain.

This protects the brain from any sudden surge of blood.

To watch these graceful creatures stoop for a drink is fascinating.

For their heads to reach the water, they must first spread or bend their front legs.

A giraffe spreads legs to drink water.

If, while in this awkward position, a giraffe senses danger, it can quickly straighten up and raise its head.

Such action should cause giddiness due to a sudden lowering of blood pressure.

Yet, in less than two seconds, Mr. Giraffe can gallop away.

An article in the Journal of Science attributed this to “the phenomenon of blood flow regulation in the giraffe head” and claimed that more research was needed to understand it.

Another phenomenon, which has long puzzled scientists, concerns the giraffe’s legs.

 “The effect of gravity,” states Scientific American, “should be expected to make the blood pressure in the legs so high that it would force fluid out of the capillaries.”

But there is no evidence of this. Giraffes do not suffer from varicose veins and edema (tissue swelling). Why is this?

Not too long ago, an international team of scientists took a fresh look at the giraffe and discovered more details about its amazing design.

They measured the arteries and found that those traveling from the heart down the legs increased in diameter and in wall thickness.

This, according to the them, prevents the “accumulation of blood in the vessels and varicose veins . . . in the giraffe’s legs.

Moreover, the thickened walls of the arteries and the thick, muscular skin around the giraffe’s legs help it to sustain the pressure.


Africa is the only continent where giraffes still live in the wild.

If you visit a game park there, you might observe these gentle giants galloping gracefully across grasslands or quietly nibbling leaves from treetops.

If so, remember Mr. Giraffe’s amazing system of blood circulation that reaches 18 feet above the ground.

And if you have the rare pleasure of watching Mr. Giraffe stoop for a drink, remember that humans are still trying to unravel his secret of coping with extreme changes of gravity.