Page 128 - Design in Nature

126 DESIGN IN NATURE

Cells of Ideal Design
Red blood cells make up the majority of all blood cells. An adult male
blood contains thirty billion red cells, which would be enough to cover
almost half the surface of a soccer field. These cells give colour to our blood
and therefore to our skin.
Red cells look like discs. Due to their incredible flexibility, they can
squeeze through capillaries and the minutest holes. If they were not so
flexible, they would surely be stuck in various areas of the body. A capillary
is normally four to five micrometres in diametre, whereas a red cell is about
7.5 micrometres (one micrometre is one thousandth of a millimetre, which is
0.000039 inch).
What would happen if red cells were not created with such flexibility?
The researchers of diabetes gave some answers to this question. In diabetic
patients, red blood cells loose their flexibility. This situation frequently gives
way to clogging with inflexible red blood cells in the delicate tissues of the
patients' eyes, which can lead to blindness.

Automatic Emergency System
The lifespan of a red blood cell is about 120 days after which they are
removed by the spleen. This loss is balanced by the continuous production
of new cells. Under normal conditions, 2.5 million red blood cells are
generated per second, a number which can be increased if necessary. A

hormone called 'erythropoietin" regulates the rate of generation. For
example, as a result of heavy bleeding due to accident or nose bleeds, the
loss is immediately balanced. In addition, the rate of generation is increased
if the oxygen content of the air is reduced. For instance, while climbing at
very high altitudes, due to the continuously declining oxygen content, the
body automatically takes this action in order to make the most efficient use
of the oxygen available.

Perfect Transportation System
The fluid portion of blood called plasma carries numerous other
substances present in the body apart from just blood cells. Plasma is a clear