Skin can contact with the external environment, divided into two layers of epidermis and dermis, which is one of the largest organs of human body. The skin is divided into three layers and five layers. The big three layers are epidermis, dermis and subcutaneous tissue, and the small five layers are stratum corneum, hyaline layer, granular layer, spinous layer and basal layer.
Skin covers the whole body surface, is one of the largest organs of the human body, accounting for about 16% of body weight. Adult skin area is about 1.2-2.0 square meters. The thickness of the thickest part of the skin is 0.5mm, the thickness of the palms and the back is the thinnest. Although the thickness of the skin varies, it can be divided into three layers: epidermis, dermis and subcutaneous tissue. The outermost layer of the skin is the epidermis, which can continuously regenerate. The epidermis is divided into five layers: cuticle, hyaline layer, granular layer, spinous layer and basal layer. The outermost skin cells are dead cells, the rest are living cells. The function of epidermis is to protect, moisturize and regenerate. The thickness of the skin on the face is generally less than 2 mm. The epidermis absorbs nutrients from the dermis and subcutaneous tissues and can produce cells.
Every day, the basal layer splits and produces cells, which push the original cells upward until keratinocytes are formed, and finally fall off. This continuous process of regeneration, migration and shedding is the metabolic process of the epidermis. It takes 14 days for a new cell to move from the basal layer to the hyaline layer. It takes 14 days for the stratum corneum to fall off, so the metabolic cycle is 28 days. Metabolism goes on every day, but it is most active at 10:00-2:00 at night. As you get older, your metabolism slows down to 60 days. Metabolism is slow, followed by many aging phenomena, skin will become rough, dull, lack of water, pigmentation.
It can be seen that the skin is divided into three layers: epidermis, dermis and subcutaneous tissue. The epidermis is divided into stratum corneum, hyaline layer, granular layer, spinous layer and basal layer. Enough to see the complexity of the skin as an organ.