And God made the beast of the earth after his kind,...
Genesis 1:25
"Having one’s head perched approximately 18 feet in the air may provide an excellent view and premium browsing options, but it does pose the problem of how to get the blood all the way up there. The higher you need to push a liquid up a pipe against gravity, the more powerful a pump you need.
Thankfully, the Creator knew about this and furnished the giraffe with a suitably large heart 2 feet
Now this is all very well for when the giraffe is walking around with its head up, but what about when it wants to take a drink? When it lowers its head, all that high pressure blood would likely rush downhill (further assisted by gravity) and blow out the delicate blood vessels in the brain and eyes—if it weren’t for a series of clever mechanisms working in concert with one another. When the head is lowered, special shunts in the arteries supplying the head restrict blood flow to the brain, diverting it into a web of small blood vessels (the rete mirabile or ‘marvellous net’). This network of vessels near the brain gently expands to accommodate the increased local blood pressure.
Valves in the jugular veins also prevent returning blood from flowing backward while the head is lowered.
All of this is controlled by a complex series of mechanisms that constantly monitor the pressure in the blood vessels and make whatever adjustments are needed to ensure that the proper pressure is maintained in all situations.
This means that even if the giraffe lifts its head up quickly mid-drink (perhaps in response to a nearby lion), proper blood supply is maintained to the brain, so that the giraffe doesn’t faint (probably much to the lion’s disappointment—a giraffe can kill a lion with its powerful kick)." CMI
