The Stratum Corneum is the uppermost of the five layers of the epidermis. It was often dismissed as the “dead cell“ layer but today we know that it has vital functions regarding mantaining a well protected healthy skin.
The structure of the Stratum Corneum:
It is made up of flattened cells called corneocytes-the bricks and intercellular substance-the mortar.
The corneocytes are protein complexes made up of tiny threads of keratin that can hold large quantities of moisture between the threads.
When the cells from the basal layer reach the stratum corneum enzymes break the outer membrane releasing fatty acis and a very important element ceramides.
The fatty acids and ceramides fuse in order to form a continuous layer of lipids.
This lipid barrier is essential to protect the skin from moisture loss, bacterial infection and environmental damage.
The ceramides are made up of a water head and and two oily tails. This allows them to attract both water and oil to the stratum corneum. However the stratum corneum is mostly made up of an oily content in order to enhance its protective properties. Ceramised are like a suit of armour they are completely indestructable.
NMF (natural moisturising factor) is also found in the stratum corneum. They are in fact only found in the stratum corneum where they act as humectants (absorbing moisture from the air). They combine this moisture with their own moisture content and allows the stratum corneum to retain its moisture despite its exposure to the elements. The lipid layer surrounding the cells helps to seal them and protect them from moisture loss.
The balance between water and sebum (oil) on the surface of the skin is essential for a healthy skin.