There’s something I just love about big things. For instance, my husband is 7 feet tall (keep in mind the giraffe in the picture is bending way down), I love big dogs, especially Great Danes, and I think giraffes are amazing. Giraffes can reach heights of 19 feet tall, making my husband look short.
Have you ever wondered how giraffes get blood up to their head more than 6 feet away from their heart? How do they bridge the distance when they stand without getting a head rush and how do they keep their head from exploding when they lean down?
Scientists once thought the giraffe had an extra-large heart to pump the blood up its long neck. This was an assumption that turned out to be incorrect. At about 25 pounds, the giraffe’s heart is average (if not a little small) when compared with other large animals.
Turns out the giraffe gets blood up to its head the same way my husband does—high blood pressure.
The key for the giraffe is in the construction of the heart. The left ventricle of a giraffe’s heart is very thick and has a small opening for pumping blood. This gives it a strong beat capable of generating twice the blood pressure of a human (about 280/180 mm Hg). Also, the heart beats faster at 150 beats per minute, again double that of a human. This creates the pressure needed to pump the blood up to the neck when a giraffe is standing.
But what about when it leans down? The giraffe has a special configuration of blood vessels called a rete mirabile that acts as a pressure-regulating system. The rete mirabile is a dense network that can temporarily re-route the blood so not all of it flows to the brain and the giraffe’s head doesn’t explode.
It amazes me to see how God designed the complex innermost parts of the stately giraffe. Perhaps my affinity for big things comes from knowing how huge and limitless our God is. Nothing is too great or overwhelming for Him to handle.
References: http://www.giraffeconservation.org/giraffe_facts.php?pgid=4, http://news.bbc.co.uk/earth/hi/earth_news/newsid_8368000/8368915.stm, http://animals.about.com/od/hoofedmammals/a/tenfactsgiraffes.htm
Photo by Janice Boekhoff 2005