Physiology Of Skin
Physiology of skin
Skin is the body’s largest organ. It covers
between 1,5 and 2 square meters and makes up nearly one sixth of body weight.
The skin not only provides a barrier against mechanical influences such as
pressure or friction, noxious chemicals, heat and cold, UV radiation and
harmful microorganisms, but is also essential for maintaining the body’s fluid
balance and sensory perception via touch, pressure, temperature and pain
receptors. From the outside inward it consists of three functional layers:
epidermis, dermis and subcutis.
The epidermis
This is the protective cover against environmental influences.
Injuries confined to the epidermis, known as abrasion, usually heal without scarring.
It’s thickness averages between 0.1 mm and 0.02 mm.
It renews itself every 28 days through continual reproduction.
Contains no blood vessels, so any bleeding indicates wounds to lower skin layers.
The dermis
Is situated between the epidermis and subcutis.
It is the connective tissue with a network of arc-shaped elastic fibres and wave-like collagen fibres, which are responsible for the high elasticity and tensile strength of the dermis.
In case of injury the fibroblasts located in the dermis start producing new collagen fibres after injury, while the elastic fibres are subject to continuous growing and decreasing.
If an injury reaches the dermis and thus involves the basal membrane, healing is normally followed by scar formation with destroyed cells being replaced by connective tissue.
The subcutis
Consists of spongy connective tissue interspersed with energy-storing fat cells, the adipocytes.
Fat cells are grouped together and held in place by collagen fibres in the form of tissue septa.
The subcutaneous tissue stores nutrients.
It insulates the body from cold and shock absorption.
Being heavily interlaced with blood cells, any kind of injury causes heavy bleeding.