Leather: Basics

The skin is the largest and heaviest organ of the human body. Its area is more than 6 square meters. The main function of the skin is protective. But its role in the body is not limited to this: the skin helps to maintain a constant body temperature, as well as to feel what is happening through the receptors located in it.

The skin has a complex structure. Each square centimeter contains 650 sweat glands, 20 blood vessels and more than 1,000 nerve endings. The thickness of the skin is only a few millimeters, but at the same time it is the heaviest organ of the human body.

Layers of skin

The skin consists of three layers: the epidermis, dermis and hypoderm.

Epidermis

Functions: growth of new skin cells, giving the skin its color, protection of underlying structures.

The epidermis is the topmost layer of the skin. It is a waterproof barrier that gives the skin its color.

Dead skin cells are continuously exfoliated on the surface of the epidermis as new cells take their place. Every day we lose about 500 million skin cells. The outer surface of the epidermis consists of 25-30 layers of dead cells.

New cells are formed in the deep layers of the epidermis. Within 4 weeks after their appearance, they move from the lower layers to the upper ones, replacing the separated dead cells.

Keratinocytes make up the main part of the epidermis. They act as a barrier protecting against bacteria, parasites, fungi, viruses, as well as from overheating, exposure to ultraviolet rays and fluid loss.

The epidermis does not contain blood vessels.

The pigment melanin, which is produced by melanocytes, gives a shade to the skin. They are located in the epidermis and protect the skin from ultraviolet light.

The epidermis consists of five layers:

• stratum corneum;
• shiny layer;
• granular layer;
• thorny layer;
• sprout layer.

Between the epidermis and the next layer of skin – the dermis – there is a thin layer of fibers, this is the basement membrane.

Derma

Functions: production of sweat and sebum, providing sensitivity, blood supply to the skin, hair.

The dermis is mainly made up of connective tissue, it protects against damage, gives the skin strength and elasticity. With excessive stretching (for example, during pregnancy), the dermis may rupture, which is externally manifested by the appearance of stretch marks on the body.

Pressure receptors (mechanoreceptors), pain receptors (nociceptors) and temperature receptors (thermoreceptors) are located in the dermis.

Also in the dermis are hair follicles, blood and lymphatic vessels, sweat and sebaceous glands. The task of the latter is the production of sebum, which lubricates and moisturizes the hair.

The dermis consists of two layers:

• Papillary (papillary) layer – consists of loose connective tissue. It creates finger-like protrusions into the epidermis, which give an uneven surface to the dermis and cause a skin pattern.
• Mesh (reticular) layer – consists of dense connective tissue, protein fibers give the skin strength and elasticity.

Hypoderm

Functions: attachment of the dermis to the body, body temperature control, fat accumulation.

Hypoderma (subcutaneous fat) is the deepest layer of the skin. Technically, it is not part of the skin, it attaches the skin to the underlying muscles and bones. Vessels and nerves pass through the hypoderm to the skin.

The hypodermis is based on adipose and connective tissues, as well as elastin, an elastic protein that is responsible for taking the original shape after stretching. The task of adipose tissue is to preserve the heat produced by the body. In addition, adipose tissue mechanically protects the underlying structures.

Some hormones and vitamin D are synthesized in the hypoderm.

Skin functions

The skin performs a huge number of functions. Some of them are:

• Protection against pathogens. The skin contains Langerhans cells, which are part of the immune system.
• Keeping. The skin retains lipids and fluid.
• Sensitivity. The skin contains nerve endings that perceive vibration, pressure, temperature, tactile, pain and other stimuli.
• Control of fluid loss. The skin prevents excessive fluid loss.
• Thermoregulation. Sweat production, dilation or narrowing of blood vessels, as well as "goosebumps" prevent the body from overheating and hypothermia.

Skin color

The skin color can vary from white to almost black. The skin tone is related to the amount of the black pigment melanin. People with fair skin have very little melanin, the color is given to it by light blue connective tissue and hemoglobin inside the blood vessels.

Melanin performs a protective function, limiting the harmful effects of ultraviolet radiation, which can cause damage up to skin cancer. Under the influence of ultraviolet light, melanocytes enhance the production of melanin to protect against it. This causes a darkening of the skin, known to us as a tan.

People living in sunny and hot regions have a darker skin color. Those who live in the cold northern latitudes have lighter skin with less melanin content.

Women tend to have lighter skin than men. It is assumed that this is due to a woman's higher need for calcium during pregnancy, and vitamin D, produced under the influence of sunlight, is necessary for its assimilation.

Skin diseases

Like any other organ of the human body, the skin is susceptible to diseases, some of them:

• Atopic dermatitis (eczema) is an inflammatory skin disease characterized by the appearance of a dry red rash with itching.
• Acne (acne rash) is perhaps the most common skin disease that develops as a result of blockage of hair follicles with sebaceous secretions and dead cells.
• Melanoma is an oncological skin disease that develops as a result of excessive exposure to sunlight.
• Rosacea is a rash on the face, more common in middle–aged people. It is characterized by a chronic course with exacerbations in the form of redness and the appearance of acne in the center of the rash.
• Psoriasis is a chronic inflammatory skin disease, the causes of which are still unknown. Psoriasis is accompanied by the appearance of peeling red foci, with the departure of scales, drops of blood appear.
• Scabies is a tick–borne skin disease accompanied by severe itching.
• Shingles is a skin disease caused by the herpes virus. Painful bubbles appear on the skin along the nerves.
• Red lichen planus is a non–infectious rash on the skin in the form of flat bumps.

Skin aging

With age, changes occur in the skin, leading to the appearance of wrinkles, a decrease in elasticity. It becomes thinner, easily damaged. Healing processes are slowing down.

The causes of skin aging are currently being actively studied. One of the proven factors is exposure to ultraviolet radiation, which also increases the risk of developing skin cancer.

Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on Medical News Today: Skin: The basics.