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Skin is vital to our overall health and wellbeing. As well as acting as the body’s first line of defense against bacteria and viruses, healthy skin maintains the balance of fluids and helps to regulate body temperature.   It is highly sensitive, recognising the softest touch as well as pain.  As our largest and most visible organ, covering nearly 2m² and making up almost a sixth of our body weight, skin condition can also have a significant impact on our self-esteem.

Skin structure

A constantly changing, dynamic organ, skin consists of three main layers - the epidermis, the dermis and the subcutis – each of which is made up of several sub-layers.  Skin appendages –such as follicles and sebaceous and sweat glands – also play various roles in its overall function.

The skin consists of three layers: epidermis, dermis and subcutis.

Epidermis

As the outermost layer that we see and touch, the epidermis protects us from toxins, bacteria and fluid loss.  It consists of 5 sub-layers of keratinocyte cells. These cells, produced in the innermost basal layer, migrate up towards the surface of the skin. As they do, they mature and undergo a series of changes.  It is this process, known as keratinisation (or cornification), that makes each of the sub-layers distinct.

  1. Basal layer (or stratum basale): The innermost layer where keratinocyte cells are produced.
  2. Prickle layer (or stratum spinosum): Keratinocytes produce keratin (protein fibres) and become spindle-shaped.
  3. Granular layer (stratum granulosum): Keratinisation begins - cells produce hard granules and, as they push upwards, these granules change into keratin and epidermal lipids.
  4. Clear layer (stratum lucidium): Cells are tightly compressed, flattened and indistinguishable from one another.
  5. Horny layer (or stratum corneum): The outermost layer of the epidermis with, on average, about 20 sub-layers of flattened, dead cells depending on where on the body the skin is. These dead cells are shed regularly in a process known as desquamation.  The horny layer is also home to the sweat gland pores and the openings of the sebaceous glands.