Page 164 - Design in Nature

162 DESIGN IN NATURE

The Pump in a Giraffe
A giraffe, with its height nearly 16.5
feet (5 metres), is one of the largest
creatures. In order to survive, the animal
has to send blood to a brain located
approximately 6.6 feet (2 metres) above the
heart. This requires an extraordinary heart
structure. Consequently, the heart of the
giraffe is strong enough to pump blood at
a pressure of 350 mmHg.
Such a powerful system, which
would normally kill a human, is contained
within a special chamber, and has been
wrapped with a web of capillaries in order
to reduce the deadly affects.
In the section between the head and the heart there is a U-shaped
system, comprised of an ascending and descending vessel. The blood
flowing in vessels of opposite direction balances itself, which saves the
animal from dangerously high blood pressures that can cause internal
bleeding.
The portion below the heart, especially legs and feet, needs special
protection. The extra thickness of giraffe skin on legs and feet prevents
adverse affects of high blood pressure. In addition, there are valves inside
the vessels that help regulate the pressure.
The biggest danger is when the animal lowers its head to the ground in
order to get a drink of water. The blood pressure, which is normally high
enough to cause internal bleeding, now increases even more. However, there
a measure has been taken against these affects. A special fluid called
cerebrospinal fluid, which bathes the brain and the spinal column itself,
produces a counterpressure to prevent rupture or capillary leakage. In
addition, there are one-way check valves which close when the animal
lowers its head. These valves reduce the flow of blood significantly, and the
giraffe can safely drink and raise its head. As a caution against dangers of
high blood pressure, the vessels of the giraffe are very thick and created in
multiple layers.