Page 126 - Design in Nature

124 DESIGN IN NATURE
Artery

Thick smooth muscle
Outer
layer Middle layer Elastic white
fibrous tissue Inner lining (endothelial
Thin smooth muscle cells)
Valve

Vein

Nuclei

Single layer of
endothelial cells
The
longest arteries
have been created to
have the strongest structure
since they are responsible for Capillary
delivering the blood rich in oxygen and
nutrients to all corners of the body. Veins are
responsible for carrying blood from the organs of the
body to the heart. Capillaries, on the other hand, have a
perfect design as they distribute the blood to the remotest places.

Haemoglobin molecules inside the red blood cells carry the oxygen.
Each one of the disk-shaped red blood cells carries about three hundred
million haemoglobin molecules. The red blood cells display a flawless
working order. They not only carry the oxygen, but also release it wherever
it is necessary, e.g. in a working muscle cell. Red blood cells deliver oxygen
to tissues, carry the carbon dioxide, which is produced after the burning of
sugar, back to the lungs and then leave it there. Following this, they again
bind to oxygen and take it to the tissues.