Skin, hair & nails

The condition of the skin, hair and nails is indicative of our health and vitality. Read more about the structure and function of our skin, hair and nails.

The skin – an important human sensory organ

When people touch each other, a fascinating concert of sensations begins. Science is in the process of rediscovering the skin.

The skin is our largest organ with a weight of up to 10 kg. At a body height of 1.70 m, it has a surface area of about 1.8 m2. The skin is also the human organism’s most functionally versatile organ. The skin forms a barrier that separates the inside from the outside. It protects against environmental influences, such as drying out, is used for representation and communication, and maintains homoeostasis (the inner balance).

The skin has important functions for the metabolism and immunology, and features a variety of adaptation mechanisms. Thanks to new imaging and biotechnology methods, the skin is being researched down to the smallest details today.

It is being revealed as a protective mantle perfected by evolution, closely interwoven with the immune system, nerves and psyche. Even the smallest malfunctions have serious effects on well-being.

The skin’s metabolism is comparatively slow, which is a big advantage when problems with the blood supply occur over short periods of time. Blood is supplied through the smallest of blood vessels. Vessels in the subcutis ensure the return flow. If the supply is disrupted for an extended period of time, the cells die off.

The skin protects the body against harmful environmental influences such as heat, cold, foreign substances and pathogens. As a sensory organ, it is important for perceiving pain and temperature changes as well as touch.

Structure of the skin

The cross-section of the human skin (cutis) can be divided into three layers. The outer layer is the epidermis. It separates the body from its environment and consists of the subcorneous, a structure of dead keratinised cells.

The dermis or true skin lies below the epidermis. Its network of collagen fibres makes the skin tremendously elastic and tear-resistant. It consists of the papillary layer and the reticular layer. The dermis is made of mobile and highly resilient fibres, tear-resistant collagen fibres and elastic fibres. The elastic fibres are responsible for the suppleness and adaptability of the skin. The dermis is also interlaced by numerous blood and lymph vessels. The cutaneous glands and hair roots mainly lie within the dermis. Most of the skin’s sensory receptors are found in this layer as well.

The lowest layer is the hypoderm or subcutis consisting of loose connective tissue and fat cells. It supplies nutrients to the upper layers. As demonstrated during a massage, it ensures that the skin as a whole is moveable. The subcutis serves as water and energy storage for the body, as heat insulation and protection against mechanical stimuli. Mechanoreceptors (Pacini corpuscles/lamellar corpuscles/Vater-Pacini corpuscles) and the hair follicles are also located in the hypoderm.

The skin and its functions

The various skin layers have different tasks: Mechanical protection is provided by the epidermis and dermis. The subcorneous protects against liquids and fluid loss, and counteracts mechanical stress. Protection for the body against bacteria is provided by the subcorneous and the acid mantle.

The subcutaneous fatty tissue is important for the storage of energy. Blood vessels, hair, subcutaneous fatty tissue and perspiration are responsible heat insulation and the temperature balance. Pigmentation provides effective protection against UV rays.

Sensory perception is an important job of the skin. Various sensory stimuli are perceived by sensory organs in the skin.

Fine nerve endings and specialised receptors in all three skin layers register pressure, distension, vibrations, cold, heat, itching or pain on the entire body and transmit messages to the brain.

The skin is the interface between the inner and outer world. This interface is where a person perceives their existence as a physical being. The sense of touch is particularly important here. Humans need physical contact.

Physiological research of the sense of touch is difficult. The entire skin covering nearly two square metres is the human sensory organ for touch. It is interlaced by a web of many millions of fine nerves and receptors.


Nails consist of hard, dense horn cells from the epidermis. They have an important purpose since they make delicate gripping possible, as with tweezers. Fingernails grow faster than toenails. Growth of 1 mm per week is typical for fingernails while toenails grow about 0.5 mm per week.

Nails protect the sensitive tips of the fingers and toes against injuries. They also play a role as tools for scratching and scoring. Nails are translucent. They are suffused with the pink colour of the nail bed underneath, which has very good circulation.

At the end of the nail (towards the body) is the lunula, light-coloured and semi-circular in shape. This white colour corresponds to the actual hue of the nail. Here the nail is not translucent. Between the lunula and the skin is the cuticle. It prevents the entry of pathogens. The nail root lies behind it (towards the body). It forms the horn cells, pushing the nail out to the front.

Skin, hair & nails

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