Page 26 - The Miracle of the Immune System

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THE MIRACLE OF THE IMMUNE SYSTEM

face. While doing this, the liquid element (cytoplasm) of the cell interior
transforms into a resistant protein known as keratin. During the process,
the cell dies. The newly formed keratin substance has a very hard struc-
ture and is not therefore subject to decomposition by digestive enzymes,
which is a sign of its resistance. Thus, invaders such as bacteria and fun-
gi will be unable to find anything to rip off from the outer layer of the
skin.
Moreover, dead outer cells containing keratin are constantly shed
from the skin surface. The new cells that come from beneath to replace the
discarded ones form an impenetrable barrier in that area.
The organisms on the skin fulfill another protective function of the

skin. A group of harmless microbes live on the skin, which have adapted
to its acidic medium. Feeding on the leftovers stuck on the keratin of the
skin, these microbes attack all kinds of foreign bodies to protect their feed-
ing site. The skin, as the host of these microbes, is like a supplementary
force that provides external support to the army within the human body.

This picture, which is magnified 5900 times, shows the cells in the trachea
(blue). They use their glands (yellow) to secrete a substance that traps the
particles in the air.