The structure and function of facial skin

Many people do not know the structure and function of their facial skin, so even if there are some problems with their face, they have no way of knowing, so they need to pay more attention to this issue. Generally speaking, the skin is divided into the surface and deep layers. If there is a problem with the surface, it can be improved well with simple care, but if there is a problem in the deep layer, comprehensive treatment is required.

[1] Skin refers to the tissue covering the muscles on the body surface and is the largest organ in the human body. It mainly undertakes functions such as protecting the body, perspiring, sensing cold, heat and pressure. The skin covers the entire body and protects various tissues and organs in the body from physical, mechanical, chemical and pathogenic microbial invasions. The skin of humans and higher animals is composed of three layers: epidermis, dermis, and subcutaneous tissue.

The total weight of skin accounts for 5% to 15% of body weight, with a total area of ​​1.5 to 2 square meters. The thickness varies from person to person and from part to part, ranging from 0.5 mm to 4 mm. The skin covers the entire body and protects various tissues and organs in the body from physical, mechanical, chemical and pathogenic microbial invasions.

The skin has two barrier functions: on the one hand, it prevents the loss of water, electrolytes, and other substances in the body; on the other hand, it prevents the invasion of harmful substances from the outside world. The skin maintains the stability of the human body's internal environment and is also involved in the body's metabolic process. Skin has several colors (white, yellow, red, brown, black, etc.), which mainly vary according to race, age and part of the body.

The skin is composed of the epidermis, dermis and subcutaneous tissue, and contains accessory organs (sweat glands, sebaceous glands, nails, toenails) as well as blood vessels, lymphatic vessels, nerves and muscles.

The skin is the largest organ in the human body. The expanded area of ​​an adult's skin is about 2 square meters and its weight is about 16% of the body weight. The thickest skin is on the soles of the feet, which is 4 mm thick, and the thinnest skin is on the eyelids, which is less than 1 mm.

epidermis

The epidermis is the outermost layer of the skin with an average thickness of 0.2 mm. It can be divided into 5 layers from the outside to the inside according to the different development stages and morphological characteristics of cells.

1. Stratum corneum: It is composed of several layers of cornified cells and contains keratin. It resists friction and prevents the extravasation of body fluids and the intrusion of chemicals. Keratin has strong water absorption capacity and its water content is generally not less than 10% to maintain the softness of the skin. If it is lower than this value, the skin will become dry and scaly or cracked. The thickness varies greatly due to different parts of the body. For example, the eyelids, foreskin, forehead, abdomen, elbows and other parts are relatively thin, while the palms and soles are the thickest. The cells of the stratum corneum have no nucleus. If the nucleus remains, it is called parakeratosis.

2. Luminous layer: It is composed of 2 to 3 layers of flat transparent cells with dead nuclei and contains keratin. It can prevent the passage of water, electrolytes and chemicals, so it is also called a barrier belt. This layer is most obvious on the palms and soles.