THE 'UP-TIGHT' GIRAFFE

At 5.5 metres, the giraffe is the world’s tallest land mammal, but how does enough blood reach a brain way up there? It has the highest blood pressure of any animal.

The giraffe's heart is not exceptionally large, weighing 10 kgs and about 60 cm long, but it powerfully pumps 75 litres per minute, at a pressure (~280/180 mm Hg) double normal and at ~170 beats per minute – nearly 3 beats per second!

Okay, so when a giraffe splays its front legs and lowers its two metre long neck to drink why doesn't the brain burst under so much pressure?

The elastic arteries of the neck contain unique valves which prevent a sudden rush of blood to the brain, with any surplus absorbed in the skull by a special pressure equalizing sponge known as the rete miribale, meaning 'wonderful net'. (Phew!!...that’s handy)

Meanwhile the legs are encased in tight skin like a fighter pilot's G-suit, to prevent them swelling.
(So who designed pressure suits first?)

Look out!!

Won't the giraffe now faint when it tries to escape quickly?

No problem. The arterial valves suddenly open and the veinous valves constrict, restoring pressure to the brain, while the rete miribale releases that surplus blood.
Every exigency has been thought of by the Designer.

So next time you’re feeling ‘UP TIGHT’, snatching sleep when you can - check in the mirror – you might see a giraffe! Now that wouldn’t be so bad you know – your 50 cm long tongue will save you cleaning your ears with cotton-buds!  (Aw…YUK!)  

 

Acknowledgements:   giraffeconservation.org            
wikipedia.com

Image credits:                                                                 
Giraffe stamp / Lorinda Taylor; Taronga Conservation Society Australia; Australia Post          

G-suit / flightgear.dk                                                                
Giraffe drinking / flickr.com                                                
Giraffe’s tongue / blog.naver.com