How many layers is the human epidermis? What are they called?

**It can be divided into epidermis, dermis and subcutaneous tissue. The details are as follows:

1. Epidermal layer: the outermost layer is the stratum corneum, and then there are the transparent layer, the granular layer, the muscle cell layer and the basal layer. The basal layer is the main germination of epidermal cells, and all epidermal cells are produced by the metabolism of cells in the basal layer, and below the basal layer there is a basement membrane belt separating the epidermis and dermis;

2. Dermis: It is divided into superficial dermis and deep dermis. **The treatment mainly focuses on the care of the epidermis and the superficial dermis;

3. Subcutaneous tissue: subcutaneous tissue includes fat layer and fascia layer.

Human ** is divided into two layers: epidermis and dermis.

The epidermis is located in the outermost layer of the town and is a keratinized stratified squamous epithelium, which differentiates from the ectoderm and occurs through which the appendages occur. The epidermis includes keratinocytes, melanocytes, Langerhans cells, and Merkel cells. The most important role of the epidermis is to form the external barrier of the body, and at the same time it has absorption and immune functions.

The dermis is a dense connective tissue differentiated from the mesoderm and has many elastic fibers and collagen fibers, so it is elastic and tough. The dermis is thicker than the epidermis and is rich in blood vessels and nerves. **There is subcutaneous tissue underneath, which is loose connective tissue with a large number of fat cells.

There are also many appendages such as hair, sweat glands, sebaceous glands, nails, etc.

The epidermal layer is divided into five layers, and the epidermal layer from the inside to the outside is the basal layer, the spinous layer, the granular layer, the hyaline layer, and the stratum corneum.

The basal layer is located at the lowest layer of the limb only epidermis, which is a single layer of columnar cells, perpendicular to the surface of **, arranged in a palisade-like shape.

Basal cells are the germinal layer.

The spinous cell layer consists of 4 to 8 layers of polygonal cells.

Granular layer: generally 2 to 4 layers of flat cells.

Located above the spinous layer, it is composed of 1 or 3 layers of spindle or flat cells in the thin part of the stratum corneum.

The hyaline lamina is found only in the epidermis of the palmoplantar and is located between the granular layer and the stratum corneum, and consists of several layers of flattened cells.

The stratum corneum is located in the outermost layer and consists of 5 to 15 layers of flattened non-nucleated cells.

Extended Information Functions of the Epidermis:

1. Barrier function.

The dense stratum corneum buffers the mechanical damage of foreign cultures; **The stratum corneum cells are closely arranged, the stratum corneum has less water content, **The weakly acidic environment on the surface can also mechanically resist the invasion of microorganisms; Melanocytes, non-keratinocytes in the epidermis, secrete melanin that protects the skin from ultraviolet rays and acts as photoprotection.

2. Absorption function.

**Absorption is carried out mainly through three pathways: stratum corneum (main pathway); hair follicles, sebaceous glands; Sweat pores.

It has the ability to absorb external substances, and it is also the physiological basis for percutaneous absorption**topical drugs.