How does the skin work?

The skin is the body's largest organ and has many important functions. One of the most vital roles is to protect us from infections and harmful chemicals. A healthy skin barrier is crucial for carrying out this task. The skin has an amazing ability to repair itself and in most cases, it's about removing what shouldn't be on the skin so that it has the conditions to heal. You should avoid unnecessary skin products such as preservatives and perfume. 

The skin's three layers

The skin is made up of three layers. These are called the epidermis (outer skin), dermis (middle skin) and hypodermis (subcutaneous tissue). Each layer is made up of several sublayers, and the different layers are structured in different ways and consist of different tissue types and cells.  

Epidermis

Epidermis is covered in fat (lipids) and water that together form a protective film (the hydrolipid film). The hydrolipid film helps keep the skin taut and also provides extra protection against bacteria, viruses, and fungi. Secretions from the sebaceous and sweat glands maintain the hydrolipid film. The epidermis is made up of keratinocyte cells in five sublayers. The cells are created in the innermost layer of the epidermis and move upwards toward the skin's surface over their lifetime. Along the way, the cells change and mature, a process called keratinization or cornification. Keratinization is what distinguishes the different sublayers. 

Dermis

Dermis is made up of connective tissue, fibers, and proteins (collagen & elastin) that contribute to the skin's elasticity and strength. The number of elastic fibers decreases as we age, which leads to the skin becoming less taut and more wrinkled. The fibers can be damaged by the sun's rays, accelerating skin aging. The dermis also contains sweat and sebaceous glands, blood vessels, sensory receptors, and hair follicles. When touched, information is sent from the dermis to the brain via nerves. The blood vessels supply nutrients and remove waste products. The dermis has a strong structure that protects the body from impacts, and the connective tissue helps wounds heal.   

Hypodermis

Hypodermis is the innermost and thickest skin layer, made up of blood vessels and connective tissue containing fat cells. The fat cells are the body's energy reserve and help regulate body temperature, as well as cushion impacts. The amount of fat we have in the hypodermis depends on our genes. The thickness of this skin layer can vary greatly. In a lean person, the hypodermis can be 2–10 mm thick, and in a person with a lot of body fat, it can be 10 cm thick.  

Why is it so important for our health?

The innermost layer of the epidermis is called the stratum basale (growth layer), and this is where keratinocyte cells are created. The growth layer consists of a single layer of tightly packed, brick-shaped keratinocytes. The next layer is called the stratum spinosum (spinous layer), and this is where the keratinocytes produce keratin, a type of protein fiber, and take on a spiny, pointed appearance.

The following layer is called the stratum granulosum (granular layer), and this is where keratinization begins. The keratinocytes produce granules that transform into keratin and lipids. The penultimate layer of the epidermis is called the stratum lucidum (clear layer), here the cells are flattened and tightly packed, making them difficult to distinguish. 

The final and outermost layer of the epidermis is called the stratum corneum (horny layer), and here there are approximately twenty layers of dead skin cells, though this varies depending on the body part. Exposed skin, such as that on the soles of the feet, develops a thick horny layer, and calluses can form. Skin that is less exposed, such as that on the eyelids, has a thinner horny layer.

The pores of the sweat glands and the openings of the sebaceous glands are also located in the horny layer. The cells in the horny layer are held together and bound by lipids. Lipids are essential for maintaining healthy skin, as they build the skin's protective barrier and lock in moisture. If you do not have enough lipids, the skin can become dry and feel tight and rough.

The horny layer protects against external factors such as cold. The dead cells are slowly worn away in a process called desquamation. The cells that are lost during desquamation are replaced by new cells. The average lifespan of a skin cell is about 4 to 6 weeks. The journey of a keratinocyte from the growth layer to the horny layer takes about 3 weeks, and then it stays in the horny layer for about 2 weeks before being worn away.