It binds the corneocytes together, ensuring the impermeability of the stratum corneum and limiting insensible water loss. It is synthesized by keratinocytes* during their maturation from the basal layer to the stratum corneum and by the secretion of sebaceous glands. The role of lipid cement is therefore protective, hydro-retentive or anti-dehydration, with particular importance for ceramides, polar lipids mostly present. It is the cement of the protective wall that is the skin.
* corneocytes : dead and flattened cells that are eliminated by desquamation, it is the superficial renewal of the skin. These are the cells resulting from the maturation of keratinocytes, which change their name at the horny layer.
* Keratinocytes : the majority of the cells that make up the epidermis (80%) are born in the first sub-layer, the basal layer, and are constantly renewed according to a cycle of 21 to 28 days. They differentiate progressively and during their maturation, release NMF (natural moisturizing factors) and epidermal lipids.