THE INNATE IMMUNE SYSTEM - PHYSICAL BARRIERS

I like to think of our bodies as being a fortress or a castle.

If that is so, then you can think of skin as being the walls of our castle or fortress.

Skin, when it is intact, is an excellent barrier to all forms of micro-organisms and other foreign matter.

However, just like castle walls have weak points in them, so our skin has several weak points, which could potentially lead to entry into our bodies by infectious micro-organisms.

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Luckily, our bodies have a way of managing to minimise the risks of infection through these weak points.

You will notice that the there is a weakness where the passages from the external environment lead to the internal body environment.

What do these passageways all have in common?

Well, with the exception of the eyes and ears, all of these passageways are lined with mucosal membranes, and these membranes are quite tough.

But, more importantly, mucosal membranes secrete various chemicals that help in our fight against infections, and you will learn more about this in the next section.

Obviously, through accident or design, the skin/castle walls can always be breached in other ways, for example cuts and operations.

The immune system has another way of dealing with these breaks through the skin, and that is by the process of inflammation (which we will look at later on)