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A basic law of physics states that pressure at the bottom of a fluid column is equal to the height of the liquid multiplied by its density. At the bottom of a 10 foot deep lake the pressure is equal to the density of water (62.4 pounds per cubic foot) times the height. In this case the pressure would be 624 pounds per square foot higher than normal air pressure. That’s why your ears pop when you dive deeply into a lake.
In the human body, the same thing is true. A man 6 feet tall will have 62.4 pounds per cubic foot times 6, or 374.4 pounds per square foot more pressure in the blood vessels in his feet than in the top of his head. That is the reason for varicose veins. You can see the design wisdom of the brain being in the top of the head rather than in the lower extremities. With lower fluid pressure, there is a reduced risk of aneurysm or breaking of a blood vessel.
The giraffe is the tallest of all living land animals. Male giraffes can be 16 to 18 feet tall (4.8 to 5.5 meters). Pressure differences between the top of the giraffe’s head and the bottom of his feet can reach over a thousand pounds per square foot. How are the pressure problems resolved in these tall creatures?
In the neck of the giraffe there are a series of one-way valves that keep the blood moving upward against the gravitational pressure. This helps the giraffe’s large heart to accomplish the job of getting the blood all the way to the brain. But giraffes drink large quantities of water for which they have to bend down. No problem -- the giraffe has a complex pressure regulating system that prevents excessive blood flow to the brain which could kill him.
But why doesn’t the blood pressure in the giraffe’s legs cause varicose veins or even ruptured veins? That problem is also covered by design. Giraffes have very tight skin on their neck and legs to prevent pooling of blood. This tight skin acts like a G-suit worn by combat pilots or astronauts who are subjected to excessive G forces or tight elastic stockings worn by people with leg circulation problems.
The giraffe is certainly well designed in its ability to handle high gravitational pressures in its cardiovascular system. Dandy designs like this one require a wise Designer.
References-
Nature magazine Sept. 3, 1987, p. 59
Wikipedia, “giraffe”, “g-suit”
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