This is the last of Skin Facts series and as we come to a close in 2015 and usher in 2016, one Skin Fact to look at is how our skin renew itself. The dermatological terms are ‘epidermal cell proliferation‘ which takes into account the turnover of cells and there are differences between normal adult, baby and eczema skin. Here’s a look at Skin Renewal Facts!
Basics of Skin Renewal
The skin regenerate itself every 27 to 39 days, meaning that the cells from the lower layer of the epidermis (outer layer) move up to the surface and differentiate. The epithelial cells are called keratinocytes and they have different structures within the different layers of the epidermis (from the deeper basal layer, to spinous, granular to the corny layer at the surface). The top layer is also known as the stratum corneum, for which we have looked into the transepidermal water loss through stratum corneum.
This skin renewal is not related to wrinkles as wrinkles are primarily due to the loss of collagen, which is in the dermis (middle layer) of skin. Baby skin feels ‘softer’ and more elastic likely due to shorter collagen fibres.
Baby Skin – Cell Turnover Rate
Microscopic examination of baby skin showed that baby stratum corneum is 30% thinner than adult skin, and that baby epidermis is 20–30% thinner than adult skin. The cell size at the corny layer of the baby skin is smaller, which implies that the baby’s cell turnover rate is higher. This correlates with better wound healing in infant skin compared to adult skin. Epidermal cell proliferation rate decreases with age.
Eczema Skin – Defective Protein
As cells proliferate, there are proteins that are expressed by the skin cells. Studies have been made on various proteins and one of the most distinguishing (lack of) proteins is that of filaggrin (FLG), which serves to produce and protect the skin barrier. In people with eczema, there is lower level of FLG, resulting in flatter skin surface cells, disrupted protective fatty layer, reducing the moisturizing function of the skin and increasing water loss from the skin. Reduced FLG also increases the skin pH and leads to increased skin inflammation. It is possible that for eczema skin, the defective protein expression makes it unable to proliferate but instead ‘terminate’ at the basal layer. This has the effect of weakening the skin structure.
Here’s a recap of all the Skin Facts posts:
Cosmetics & Toiletries – Baby Skin vs. Adult Skin Structure, Function and Composition