Epidermis The skin - is the outer covering of the body. It consists mainly of epithelial tissue. The total area of ​​the skin - 1.5-2 m 2 . It

Skin structure (epidermis, dermis, hypodermis)

Epidermis

The skin — is the outer covering of the body. It consists mainly of epithelial tissue. The total area of ​​the skin — 1.5-2 m2. It has three layers (diagram 94). First, external — is the epidermis (from Greek “above” and “skin”), formed by epithelial tissue.

The upper layer of the epithelium — are a strong, thick and horny cells. This layer is called stratum corneum. This layer protects skin from mechanical and chemical damage, intrusion of water and microorganisms into the body.

In the areas of skin that are often having mechanical injury, the stratum corneum thickens, forming calluses. Horny cells are constantly flake off. Instead of them form new, capable of division ones.

Dermis

Beneath the epidermis is placed middle layer of skin — the dermis, or the skin. It has blood vessels — the receptors that respond to touching, squeezing, as well as pain, cold and heat, and it also has different appendages and pigment cells. The latter contain a dark pigment — melanin (“black” from Greek). When a person tans, the amount of melanin in the cells is greatly increased, and the skin becomes brown. The dermis contains many elastic fibers arranged in a certain direction. Therefore, the so-called skin pattern, especially the fingertips — is individual. The uniqueness of the fingers skin pattern is used in court practice for identification (fingerprinting). When a person is aging, the elastic fibers partially lose water, reduce in size and the skin wrinkles. Taken from http://worldofschool.org

Diagram 94. The structure of the skin and hair: 1 — epidermis; 2 — the dermis; 3 — subcutaneous fat; 4 — the root of the hair; 5 — hair bulb; 6 — artery; 7 — vein; 8 — sweat gland; 9 — the hair shaft; 10 — nociceptors; 11 — sebaceous gland; 12 — the muscle that raises the hair; 13 — collagen fiber; 14 — mechanoreceptor; 15 — fiber sensory nerves; 16 — fiber vegetative nerves

Hypodermis

Under the dermis there is a third, the deepest layer — subcutaneous tissue (hypodermis), consisting of fat. It protects the body from mechanical damage, retains internal heat, and it is a place of energy substances (fat) accumulation.

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Questions:
  • Identify the features of the skin structure.

  • Explain the origin of the word "epidermis".