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:
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
bacteria
Ø Chemical substance dangerous to the
living cell.
living cell.
The
underlying layers are concerned with the replacement of the outer layers to
counter wear and tear.
underlying layers are concerned with the replacement of the outer layers to
counter wear and tear.
The epidermis as a guard
against harmful rays
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.
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.
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
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.
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 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.
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.
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.
