Hard-working Hearts

The Heart of the Matter

Because giraffes are so tall, their hearts must be capable of pumping blood at a high enough pressure to flow up through their necks and into their brains. For this reason, a giraffe’s heart has special adaptations to overcome gravity. A giraffe’s heart can weight up to 25 pounds, and is several inches thick, making it very powerful. Additionally, a giraffe’s heart pumps around 16 gallons of blood per minute!

Giraffe heart

These strong hearts also produce an average blood pressure of 280/180, which is twice the pressure of other large mammals, and more than twice the recommended human blood pressure of 120/80. This high blood pressure is necessary for blood to reach the brain, but could be dangerous when a giraffe lowers its head. For this reason, giraffes have a pressure-regulating system made up of small blood vessels called “rete mirabile,” anti-pooling valves, and reinforced artery walls. This complex system prevents excessive amounts of blood from rushing toward a giraffe’s brain when it lowers its head. The jugular veins in giraffes also have valves that stop blood from flowing backwards into the head when its lowered. 

Interesting fact of the week: Giraffes have heart rates of around 150-170 beats per minute!    

Work's Cited

Bourton, Jody. "Supercharged Heart Pumps Blood Up A Giraffe's Neck." Earth News. BBC, 20 Nov. 2009. Web. 08 Apr. 2012. <http://news.bbc.co.uk/earth/hi/earth_news/newsid_8368000/8368915.stm>.

"Facts About Giraffes." About.com: Animals / Wildlife. Web. 05 Apr. 2012. <http://animals.about.com/od/hoofedmammals/a/tenfactsgiraffes.htm>.

"Giraffes- All You Never Wanted to Know." Squidoo. Web. 08 Apr. 2012. <http://www.squidoo.com/giraffes-all-you-never-wanted-to-know>.