Skin

With a surface area of 1.5–2 m², the skin is the largest organ of the body. The skin consists of different layers: the epidermis, the dermis, and the subcutaneous connective tissue. Each layer has a different function.

The skin is a versatile and indispensable organ. The skin protects the body, among other things, against harmful external influences such as pathogens and sun rays, prevents dehydration, and enables us to feel temperature and pain.

Epidermis

The top layer of the skin is the epidermis (epidermis). This is the visible part of the skin and is in most places only a few tenths of a millimeter thick. This layer protects the body against harmful external influences, such as dehydration, sunlight, and the penetration of dangerous (liquid) substances. Bacteria, fungi, and viruses are also kept out in this way.

The epidermis renews itself continuously. This process is faster in young people than in older people and ensures that a wound closes again fairly quickly. The epidermis itself consists of 2 different layers. From the outside in, these are:

• The horny layer. This mainly contains dead skin cells that protect the body. In areas with a lot of callus, the horny layer is extra thick. This is often visible and palpable on the soles of the feet and the palms of the hands.
• The germinative layer. New skin cells are produced here that slowly move toward the surface. The pigment cells are also located in this layer. They determine how dark the skin is and protect against sunlight.

Dermis

The middle layer is formed by the dermis (dermis). The dermis is a 1-3 mm thick layer of connective tissue. This layer provides the strength and elasticity of the skin. The older the skin, the less stretchable and strong it is.

In the dermis lie the so-called skin appendages, such as the sebaceous glands to lubricate the skin (not on the palms and soles), sweat glands, small lymph vessels to remove waste products, hair roots, and the nail bed. In addition, small blood vessels and nerves are found here. These ensure that the skin is well perfused and provide sensation (touch, temperature, and pain) at that spot.

Subcutaneous connective tissue

The deepest skin layer is the subcutaneous connective tissue (subcutis). This layer consists mainly of fatty tissue interwoven with connective tissue and provides protection for the underlying organs and body parts. In addition, fat is an important storage place for energy, serves as an insulating layer, and thus plays a role in maintaining body temperature.