Besieged Castle: The Human Body
is a fact that even though we try to live in clean environments,
we share these places with many micro-organisms. If you
had the chance to view the room you are currently sitting
in with a microscope, you would immediately see the millions
of organisms you live with.
this situation, the individual resembles a "besieged
castle". Needless to say, such a castle, which is surrounded
by countless enemies, must be protected in a very complete
and organized manner. Human beings are created along
with this perfect protection they need, and are not,
therefore, entirely defenceless against these enemies.
The "micro" guards in our bodies never leave us alone
and fight for us on many fronts.
The invader cells that
want to take control of the body first have to fight
their way through the front line of the body. Even though
these fronts have their weaknesses at times, the enemy
is hardly ever allowed to pass through them. The first
front the enemy must penetrate is our skin.
The Protective Armour of Our Body:
The skin, which covers the entire
body of a human being just like a sheath, is full of
amazing features. Its ability to repair and renew itself,
its non-permeability by water, despite the existence
of tiny pores on its surface as opposed to its function
of discharging water through perspiration, its extremely
flexible structure, allowing free movement, as opposed
to its being thick enough to avoid easy rupture, its
ability to protect the body from the heat, the cold,
and harmful sunrays are only a few of the features of
the skin that have been specially created for human
beings. Here, we will deal with a particular feature
of this extraordinary wrapping paper: its ability to
protect the body from disease-causing micro-organisms.
If the body is considered a castle besieged by enemies,
we can safely refer to the skin as the strong walls
of this castle.
The main protective function
of the skin is realized via the dead cell layers constituting
the outer section of the skin. Each new cell produced
by cell division moves from the inner section of the
skin towards the surface. 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 structure and is not therefore subject
to decomposition by digestive enzymes, which is a sign
of its resistance. Thus, invaders such as bacteria and
fungi 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 feeding 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.
first defense response of the organism against
its dangerous invaders is the rapid self-repairing
of the skin tissue following the infliction of
a wound. When such a wound ruptures the skin,
defence cells immediately travel to the injured
area to fight with the foreign cell and to remove
the debris of the affected tissue. Later, some
other defence cells enhance the production of
fibrin, which is a protein that rapidly re-covers
the wound with a fibrous network. This picture
is of a fibrin that has spread over some red blood
IN-DEPTH VIEW OF THE SKIN
Above is a cross-section of
the skin. The sweat droplets secreted from the skin
play a variety of roles in the body. In addition bringing
down the body temperature, they provide nutrition for
certain bacteria and fungi living on the surface of
the skin, and produce acidic waste materials such as
lactic acid which helps decrease the PH level of the skin.
This acidic medium on the skin surface creates a hostile
environment for any harmful bacteria that are looking
for a place to live.
is a close-up of the sweat gland entrance.
Here, too, you will find bacteria just like
everywhere else on the skin.
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.
you can see the macrophages located in the
lung tissues. They eliminate the dust particles
in the air we inhale.xxxxxxxxxx