The epidermis is the outermost layer of your skin.
It is a waterproof, protective barrier and plays a critical role in skin rejuvenation.
The epidermis was once considered a superficial shell, but discoveries about the psychological processes in our skin, have found it to be so much more.
Many changes occur deep within this layer; changes which are due to ageing, stress, UV, environmental pollutants and chemicals, and poor lifestyle habits such as smoking and drinking.
What is the epidermis?
The prime function of the epidermis is to act as a physical and biological barrier to the external world, preventing penetration by irritants and potential allergens; at the same time, it prevents the loss of water and maintains your internal homeostasis.
New cells are made in the lower layers of the epidermis, and over the course of around 4 weeks, these cells make their way to the surface, where they become flat and hard, replacing dead cells; literally, millions of these skin cells are shed daily.
Keratinocytes are the most common cell type within the epidermis; their job is to act as a barrier against bacteria, parasites, fungi, viruses, heat, ultraviolet (UV) rays from the sun, and water loss.
The colour of your skin is produced by a pigment called melanin, which is produced by melanocytes; these are also found in the epidermis and help to protect your skin from UV rays.
Interestingly, the epidermis contains no blood supply of its own, which is why you can shave your skin and not cause any bleeding, despite losing many cells in the process.
The epidermis is composed of five layers
- stratum corneum is the outermost layer
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum germinativum
The epidermis and its role in skin health
The keratinocyte cells are created at the junction, between the epidermis and the dermis. When they are ready, they begin a month-long journey towards the top of the epidermis, the outermost layer of your skin referred to as the stratum corneum.
When they begin their journey, they are plump and healthy, but as the keratinocyte cells begin to move towards the surface, they break down, becoming flat and hard, where they fill with a tough protein known as keratin.
This protein gives your skin it’s waterproof covering, protecting you from the outside world, preventing the absorption of many substances through your skin and potential viruses and bacteria.
Once at the surface, they start to shed; this is a continuous cycle as new cells move towards the surface. Whilst 95% of these cells are there to make way for new cells; there are around 5% that contain melanin which helps to determine our colour, the darker the skin, the more of these cells there are.
So as we can see, the epidermis is the outermost layer of your skin, which serves as a physical barrier, protecting your body against external aggressions such as cold temperatures, UV and bacteria. The rest of the epidermis mostly serves the role of producing the skin barrier.
A little known fact is that the interaction between cells in the epidermis and cells in the dermis is so strong, that cells within the dermis actually influence the way the epidermis functions, this regulates its ability to create healthy new cells and clearer skin.
This article, a guide to the physiology of the layers of the skin, contains some interesting facts on the epidermis.