Normal skin layer structure and its physiology
The color of the skin will alter according to age, sex and health. Underneath the dermis layer of the skin, it consists of a large amount of blood vessels, nerves, lymph, hair follicles, sebaceous glands, sweat glands and many different types of organizations. Skin is the body's largest organ, and the thickness of this organ would alter according to age and location of the skin. There are many skin grooves on the surface of the skin, mainly due to dermal fiber bundles arrangement and traction. Skin grooves turn the surface of the skin into thin, parallel at the same time uplifting the skin ridges. Deeper skin grooves constitute the polygon area known as the skin field. These three structures are normal physiological structure of skin, and is not caused by external or internal factors nor wrinkles, and should pay more attention to it.
Epidermis is located in the outermost layer of the skin, it can be divided into five layers from the most outer layer to the most inner layer, they are the stratum corneum, transparent layer, granular layer, acanthuses and basal layer, and they consist of keratinocytes and dendritic cells. The skin’s role is to stop the invasion of foreign material from the external environment and to prevent bacteria and chemicals penetration inside the body.
1) Cuticle Layer: Consists of 10 layers of stratified dead squamous cells, keratin and protein link the dead cells together in order to protect skin, prevent water evaporation and prevent skin breakage, the dead skin cells will naturally fall off.
2) Transparent Layer: Consists of several layers of transparent cells, they can reflect sunlight to prevent water evaporation and dissipating.
3) Granular Layer: Consists of two to three-flat layers dying cells, they turn into a granular keratin material, known as keratin.
4) Acanthuses Layer: Contains many sensory nerve endings that can sense stimuli, is the thickest layer of the epidermis.
5) Basal Layer: It is the source of epidermal cell division; it has reproductive capacity, and consists a layer of closely arranged cells.
Located between epidermis and subcutaneous fatty tissue, its thickness is a bout 1-2mm, accounts for nearly 95% of total skin thickness, including the papillary layer and reticular layer, it is composed of connective tissues interwoven vertically and horizontally, it consists mainly of collagen fibers and elastic fibers which provides the skin its elasticity and tension. Dermis supports and protects the internal organizations, it also increases the skin's elasticity and immune support, and furthermore, it is used to nourish the skin and provides moisturizing function. Dermis has a significant role in beauty.
1) Upper dermis: It is the thinnest layer that is located on the upper layer of the dermis. Uplifted epidermis staggered many areas. Between the uplifted areas include blood vessels, and lymphatic capillary networks and sensory nerve endings.
2) Lower dermis: It is the thicker layer that is located in the lower dermis. It consists of mainly collagen fibers, elastic fibers and reticular fibers. Elastic fibers have with strong flexibility, and provide elasticity to the skin, but if the elastic fibers are lost, wrinkles would appear.
Includes the sebum layer, which contains blood vessels, sweat glands, sebaceous glands, hair follicles, lymphatic and nervous. It is flexible, and can buffer external shocks, therefore providing a protection function to the body tissue. The sebaceous glands secrete sebum which is an organic acid mixture; it contains a variety of lipids, including saturated and unsaturated fatty acids, glycerides, sterols, squalene and other substances. On the skin surface, sebum forms a layer of leather which covers the lipid membrane, called the skin surface lipid membrane, its role is to lubricate the skin and maintain moisture, and preventing dryness caused chapped skin. Excessive subcutaneous fat, obesity, or too skinny will change the skin to be loose and lack of luster. Nowadays, people think that being thin equals to being beautiful, but excessive weight loss, reduces subcutaneous fat, actually causes a great damage to the skin, which not only turns the skin loose and causes wrinkles, but also the skin will lack its gloss and its elasticity.