Epidermis as a protecting guard

                                     Epidermis

The outer layers of the epidermis are the body’s frontier to the outside world protecting  the living tissues within from the ravages of the environment:

Ø The drying effect of air

Ø Harmful rays of the sun

Ø Harmful microorganism particularly bacteria

Ø Chemical substance dangerous to the living cell.

The underlying layers are concerned with the replacement of the outer layers to counter wear and tear.

The epidermis as a guard against harmful rays

The horny layer is greatly involved in protecting the body against the ultra violet rays of the sun which in excess are lethal to living cell.

                                  The rays are partially reflected by each of the layer of horny layer cell so that very little penetrates the full thickness of the epidermis; the brown layers pigment of the skin is also involved in screening against ultra violet.

The epidermis as protection against bacteria

              The horny layers acts as physical barrier against entry of bacteria. There are however pores in the horny layer notably the hair follicles, through which bacteria can gain entry. The sebum and the sebaceous gland are able to prevent their entry. The sebum on the skin is deliberately acidic and bacteria are inhibited by acids. The sebaceous glands are able to destroy any bacteria that might enter them through the hair follicles.

Epidermis guard against the entry of chemicals

                              The sebum covering the skin is basically hydrophobic tends to discourage not only water but also water soluble chemicals from passing through it. The keratin of the horny layer is essentially hydrophilic and similarly tends to hinder the passage of oils and oil soluble substance into the skin.

                   Between them they from a barrier to the entry of chemical substances through the   skin. The barrier is however for from perfect and the skin is permeable to a wide variety of substances. Hence there is an irritation system which should respond when undesirable substance do enter.