How does the skin work?

The skin is the body's largest organ and has many important functions. One of the most important tasks is to protect us from infections and dangerous chemicals. A healthy skin barrier is essential to get the job done. The skin has an amazing ability to repair itself and in most cases it is a matter of removing what should not be on the skin so that it gets the conditions to heal. You should avoid unnecessary additives on the skin such as preservatives and perfumes. 

The three layers of the skin

The skin consists of three layers. These are called epidermis (upper skin), dermis (skin) and hypodermis (under skin). Each layer consists of several layers and the different layers are structured in different ways and consist of different tissue types and cells. 

Epidermis

The epidermis is covered by fat (lipids) and water, which together form a protective membrane (hydrolipid film). The hydrolipid film contributes to keeping the skin resilient and is also an extra protection against bacteria, viruses and fungi. Secretions from sebum and sweat glands maintain the hydrolipid film. The epidermis consists of keratinocyte cells in five layers. The cells are created in the inner layer of the epidermis and move during their lifetime up to the surface of the skin. During the journey, the cells change and mature, which is called keratinization or keratinization. Keratinization is what separates the different layers. 

Dermis

The dermis consists of connective tissue and fibers as well as proteins (collagen & elastin) which contribute to the skin's elasticity and strength. The elastic fibers become fewer in number as we get older, which leads to the skin becoming less elastic and wrinkled. The fibers can be damaged by the sun's rays and age the skin prematurely. The dermis also consists of sweat and sebum glands, blood vessels, sensory bodies and hair follicles. When touched, information is sent from the dermis to the brain via nerves. The blood vessels supply nutrients and dispose of waste products. The dermis has a strong structure that protects the body against impacts and the connective tissue helps wounds heal.  

Hypodermis

Hypodermis is the innermost and thickest skin layer consisting of blood vessels and connective tissue containing fat cells. The fat cells are the body's energy reserve and help to regulate body temperature, but also to absorb shocks. How much fat we have in the hypodermis depends on which genes we have. 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 fat, it can be 10 cm thick. 

Why is it so important for our health?

The innermost layer of the epidermis is called the growth layer (stratum basale) and here the keratinocyte cells are created. The growth layer has a cell layer of densely growing brick-shaped keratinocytes. The next layer is called the spiny cell layer (Stratum spinosum) and this is where the keratinocytes create keratin which is a protein fiber and takes on a spiky/pin shaped appearance.

The following layer is called the granular layer (Stratum granulosum) and this is where keratinization begins. The keratinocytes create granules that are converted into keratin and lipids. The penultimate layer of the epidermis is called the bright layer (Stratum Lucidium), here the cells are flattened and tightly packed, which makes it difficult to distinguish them.

The last and outermost layer of the epidermis is called the stratum corneum, here there are approximately twenty layers of dead skin cells, but this varies depending on the body part. Exposed skin, such as the one on the soles of the feet, gets a thick horny layer and calluses can occur. Skin that is not as exposed, such as e.g. the one on the eyelids has a thinner stratum corneum.

The stratum corneum also contains the pores of the sweat glands and the openings of the sebaceous glands. The cells in the stratum corneum are held together and bound together by lipids. The lipids are important for maintaining healthy skin because they build up the skin's protective barrier and bind moisture together. If you don't have enough lipids, the skin can become dry and feel tight and rough.

The horn layer is a protection against external factors such as e.g. cold. The dead cells are slowly worn away in a process called desquamation. The cells that disappear during exfoliation are replaced by new cells. The lifespan of the cell is approximately 4-6 weeks long. The keratinocyte's journey from the growth layer to the stratum corneum takes about three weeks, and then it stays for about 2 weeks in the stratum corneum before being worn away.