The skin

Skin, our body’s largest organ

Many people desire beautiful skin: healthy looking, as flawless as possible and wrinkle-free.

Women of all ages put a lot of effort into this. And men are also starting to pay attention. Yet, if we look a little closer, the skin is so much more than something nice to look at. It’s much more than the body’s outer shell. At first glance, the skin may seem rather boring since all we see is its surface. Yet, it is much more complex than we often imagine. Let's take a closer look, as if under the microscope.

The skin’s structure

The skin is not only the largest organ in our body, it’s also the structure that is in direct contact with our surrounding environment. It has many functions. It not only forms a protective layer against environmental influences, it’s also visible to all of us - this is why its appearance and health are so important. It is composed of several layers, which in turn are subdivided into strata.

When we look at ourselves or others, we are looking at the outer layer, called the epidermis, which also forms the thin outermost but extremely important barrier layer called the stratum corneum. Underneath the epidermis is the dermis. The bottom layer is the subcutaneous tissue or hypodermis. The skin also contains skin-associated structures, such as hair follicles, sweat and sebaceous glands as well as nails. These are known as skin appendages (adnexa) and are derived from the skin.

Schematic diagram of the human skin
Schematic diagram of the human skin

The epidermis

The thickness of every layer of the skin varies depending on the region of the body. The epidermis is only 0.1 mm thick on average (thinner on the eyelids, thicker on the soles of the feet). If we take a look at a cross-section, we see that the epidermis is essentially made up of two main layers. The outermost layer is the stratum corneum or horny layer, which mainly consists of dead cells. These horny cells (corneocytes) are formed by keratinocytes formed in the deeper germinal layer of the epidermis.

As the cells multiply and are pushed up to the surface by newer cells, they start to change (known as differentiation) forming the horny layer’s dense network of proteins and lipids. This is often described as a brick and mortar-like structure. The upper corneocytes eventually shed making room for the next layer. We lose over 200 million skin cells a day (or about 58 kg in our lives)! The continual renewal process of the epidermis takes about 30 days (the horny layer is renewed approximately every 14 days).

Extra information:

Did you know that the dust around our house is mainly the cells we shed?

By the way, cells are very sensitive to UV rays. This is why there are specialized pigment cells (melanocytes) found in the germinal layer. UV radiation stimulates them to form a protective pigment called melanin. Melanin is then taken up and stored in keratinocytes. We notice this when we get a tan. Melanin helps protect the cells’ genetic material when the skin is exposed to the sun. 

There are no blood vessels in the horny layer and actually nowhere in the epidermis. Wherever the skin has to be more elastic, it is very thin, for example, our eyelids. The skin is thick in areas that are exposed to high loads such as hands and soles of the feet. Calluses, for example, are typical manifestations of a highly thickened horny layer. They protect the skin from damage such as prolonged rubbing and other irritations. 

The Dermis

While the epidermis enables the protective function of the skin, the dermis makes sure the skin is firm. Its two layers consist of fibers (like collagens and elastins) that provide resiliency and elasticity. The hair follicles are also anchored within the dermis.

Sebaceous glands in the dermis produce sebum to help our skin feel smooth. They are found almost everywhere in the skin, except the lips, palms of the hands and soles of the feet and are most prevalent in the face, scalp and shoulders. This is why, if too much sebum is produced, our face, scalp and hair are sometimes oily.

Ear wax is also produced with the help of secretions of both, the ceruminous and sebaceous glands. Besides that, the dermis contains our sweat glands - each of us benefits from a mere 2 to 3 million. Sweat helps regulate our body temperature and works together with sebaceous glands to create an acid mantle on the skin’s surface to keep a constant healthy pH of 5-6. 

The Subcutaneous Tissue (hypodermis)

The subcutaneous tissue or hypodermis is the connection to underlying body structures under the skin. It also contains our body fat. Often called the superficial fascia, it allows sliding movement of the skin over a wide variety of body “surfaces”: bones, muscles or tendons. 

It’s important for us to take good care of this complex organ. Everyday. Without fail. Let’s enjoy feeling good. Taking care of our well-being and how we look.