The outermost, visible layer of the skin is called the
epidermis. It mainly consists of horn-forming cells (keratinocytes), which are
slowly pushed upwards by the new cells that follow, keratinize and ultimately
die. The keratinized cells (corneocytes) are firmly glued together and seal the
skin from the outside.
The epidermis is constantly renewing itself: new cells are
created in its lower layers, which migrate to the surface within four weeks.
The constant supply of cells compensates for what is lost on the surface due to
friction and trickles down to the floor as tiny scales. When there is pressure
or friction, the cells in the epidermis divide faster. The amount of flaked
skin remains the same. As a result, the horny layer on the surface gradually
thickens - it formsCornea. This is a protective mechanism for the skin to
better withstand pressure and friction.
The balance between cell formation and peeling is rarely
disturbed by a disease: For example, infections, autoimmune or hereditary
diseases can lead to the formation of corneal flakes all over the body. If only
a single spot becomes keratinized, this can indicate white skin cancer or a
preliminary stage.
The hide varies in thickness depending on the region of the
body. For example, it measures just 0.3 millimeters at the elbows and hollows
of the knees - at other points such as the soles of the feet and palms, it is
relatively thick at up to 4 millimeters.
The hide
also contains other types of cells with special tasks:
• Melanocytes produce and store the black pigment melanin.
When sunbathing, they produce more melanin, which makes the skin darker. In
this way, the skin protects itself from the sun's harmful UV rays.
• Lymphocytes and Langerhans prison cell play an important
role in the defense against pathogens. The cells collect the pathogens, pick
them up and transport them to the next lymph node.
• Merkel prison cell are special nerve cells in the skin
that ensure that pressure is perceived.
The dermis
The dermis lies under the epidermis, firmly fused with it.
It consists of a dense network of tear-resistant, elastic collagen fibers.
These ensure that the skin is firm and stable, but also elastic. If the skin is
stretched too much, such as the abdominal skin during pregnancy , cracks can
appear in the dermis, which can be seen from the outside as light stripes.
Bulges in the dermis extend into the connective tissue,
which also envelops the muscles and bones and connects them to the skin.
The dermis is traversed by a network of nerve fibers and the
finest blood vessels, the capillaries. Nutrients and oxygen reach the cells
through these blood vessels. Your other important job is to dissipate excess
body heat. Most of the tactile cells and sweat glands are also embedded in the
dermis.
The
subcutaneous tissue
The subcutaneous tissue (subcutis) mainly contains fat and
connective tissue. Between the bulges of the dermis, the subcutaneous tissue
forms tiny cavities that are filled with storage tissue made of fat and water.
The fat acts like a shock absorber and protects the bones and joints from blows
or bumps from the outside. It also serves as a heat pad. The fat cells of the
subcutaneous tissue also form a large number of hormones - under the influence
of sunlight, for example, the vital vitamin D.
In the subcutaneous tissue as well as in the overlying
dermis there are blood and lymph vessels as well as nerves, sweat, sebum and
scent glands as well as the roots of the body and scalp hair.
