Anatomy and function of human skin

General information about the skin

The skin of the human body has a total area of 1.5 to 2 m2. The total weight is about 3.5 to 10 kg. The surface shows an individually different relief.

This relief is genetically determined. The skin is divided into two different types. On the one hand, the hairless groin skin, which is located on the inner surfaces of the hand and foot.

Here there is a so-called papillary ridge, which divides the groin skin. Thus fingerprints are created, which are genetically determined and individual for each person. The remaining skin surface is divided into irregular fields by furrows.

In these furrows of the so-called field skin lie the hairs. The skin is also divided into so-called dermatomes by sensitive nerves (emotional nerves). A dermatome is the segmental area of skin innervated (supplied) by a spinal nerve. Spinal nerves emerge from the spinal cord and run into their supply area. Each spinal nerve consists of many afferent nerve fibers that reach the skin via various peripheral nerves.

Structure of the skin

The skin is made up of several layers, which are formed from different tissues. On average our skin thickness is 1.5 to 4 mm. The skin is roughly divided from outside to inside into epidermis, dermis and subcutis.

The epidermis in turn is divided into four to five layers, depending on the type of cells found in these layers. These are from the outside to the inside: horny layer, shiny layer, granular cell layer, prickle cell layer and basal layer. The horny layer, which is located too extremely on our skin, consists mainly of dead cells.

This layer is particularly pronounced in the horny layer, which we find for example on the soles of our feet, because the skin is exposed to particular stress there. Over time, the dead cells recede from our skin, but are constantly renewed from below by new cells that are created by cell division in the basal layer. The basal layer also contains pigment-producing cells, the so-called “melanocytes”, which give our skin its color.

The shiny layer is only found in the so-called groin skin, which can be found on the palms of the hands and soles of the feet. In contrast, the skin on all other regions of our body is called field skin. It covers about 96% of our body surface.

In the epidermis, pain signals and light touches, which hit the skin from outside, are absorbed and transmitted to the brain. The dermis consists mainly of connective tissue fibers and is responsible for anchoring the epidermis. The blood vessels that are essential for the nutrition of our epidermis run through this layer.

It is also important for regulating the temperature of the skin. Hair roots, sebaceous glands and sweat glands are embedded in the dermis. Furthermore, touch and pressure sensations are absorbed in this layer and transmitted to our brain.

The dermis is divided into a papillary layer and a reticular layer. The papillary layer contains so-called papillary bodies, which are arranged in longitudinal rows in the groin skin on the palm of the hand and the sole of the foot and can thus be seen there as “skin ridges”. These “skin ridges” are the basis for our fingerprint.

The subcutaneous tissue is mainly formed by subcutaneous fat and loose connective tissue. Nerves and larger blood vessels run through it to supply the layers above. Similar to the sclera, sensory cells are found here, but they tend to absorb and transmit strong pressure sensations.

Dermatoms represent the sensory area of individual spinal nerves. A sensory area is the supply area of a nerve with sensation. This is well illustrated in the adjacent picture.

Red is the area supplied by the nerves of the cervical spine, blue the area of the thoracic spine. Failure of a nerve leads to a sensory disturbance of the skin in the exact area of the respective nerve. Our skin consists of two layers: the epidermis, the upper layer, epidermis of the dermis, the lower layer, dermis. Further under it is the subcutaneous fatty tissue.

  • The epidermis, the upper layer, epidermis
  • The dermis, the lower layer, sclera