Monday, October 21, 2013

The structure of skin

The skin is one of the biggest organs on the body. It has two main layers -
the epidermis and the dermis.
Epidermis
The structure of skin
The skin is one of the biggest organs on the body. It has two main layers -
the epidermis and the dermis.
Epidermis
This is the outer surface of the skin that we can see and feel and where we
find the hair follicles. It is made up of several layers that, together, form a
protective outer sheath. This is protected by a mixture of water and oil (sebum)
excreted from the scalp. The mixture is mildly acidic and contains 'friendly'
bacteria.
The epidermis is contstantly being worm away in a process called exfoliation.
Dead cells are shed from the skin and new, healthy cells take their place.
Dermis
This is the deep, inner layer of the sking that contains the blood and nerve
supply. On the scalp, the dermis contains the sebaceous glands that produce
sebum and the sudiferous glands that produce water. The oil and water mix
together to form a protective covering for the hair.
The dermis also contains nerve receptors that sense heat, cold and pain and
adipose tissue or fat cells.
Features of skin
The skin has a number of features. Most of these grow from the epidermis down
into the dermis. The main ones are:
  • follicles - pore-like structures that produce hair
  • dermal papilla - the origin of all cell growth and cell division
  • sebaceous glands - secrete oil called sebum that protects us against
  • bacteria, lubricates and waterproofs the skin and, on the scalp, makes our hair
    soft, shiny and pliable
  • sudoriferous (sweat) glands - excrete waste in the form of sweat, which
  • evaporates to cool the body
  • arrector pili muscles - attached to the hair follicles, these contract when
  • we get cold. This pulls the hair upright, giving us goose pimples and trapping
    warm air aForma rotunda our body to help keep us warm.
There are four main functions of the skin:
  • protection from strong sunlight and bacteria
  • sensation through the nerves
  • excretion of waste and oil to make us waterproof
  • regulation of temperature by releasing sweat to cool us and trapping air
  • aForma rotunda us to keep us warm
The natural pigment of the skin is the same as the pigment in the hair. It is
called melanin and is produced by cells called melanocytes.