Skin structure
To understand some of the mechanisms that may be involved in seasonal changes in skin, it is helpful to briefly review skin physiology.
There are three main layers in skin. The epidermis, the outer layer, measures 50-100µm thick and lies over the dermis (1-2mm), which sits on the subcutaneous tissue of the hypodermis layer (1-2mm).10
Building up from the junction with the dermis, the epidermis has a layer of basal cells (stratum germinativum), followed by squamous cells (stratum spinosum), granular cells (stratum granulosum) and finally the outermost layer of the stratum corneum. Keratinisation takes place as cells migrate up through the epidermis.11
Sweat glands and sebaceous glands sit in the dermis, while the base of the hair follicle may extend down to the junction with the hypodermis.