Skin Biology 1 Part 1: Structure of the Skin
Start of our Skin Biology series: Structure of the skin and the significance of the three germ layers
The skin, with an area of approximately 1.8 square meters, is our largest organ and protects the body from heat, light, and injuries. The skin represents the interface between the interior of the body and the external world, regulates body temperature through sweating, and can store water and fat. The structure of the skin is optimal for fulfilling its specific and diverse tasks and functions.
To better understand the most diverse skin manifestations, symptoms, and changes, in our Skin Biology series we go into detail about the biological and embryological foundations. The three germ layers endoderm, mesoderm, and ectoderm have a fundamental significance in skin biology for understanding skin symptoms and skin reactions. We explain the connections to you here.
1. Epidermis (outer skin)
The epidermis is very thin – between 0.10 and 0.12 millimeters. Its uppermost layer consists of dead, keratinized cells and is thus the first and most important protective barrier to the external world. Beneath the stratum corneum lies the germinal layer, which supplies the stratum corneum with new cells (horn cells). Beneath that lies the basal cell layer, which is structurally connected to the dermis below via various fiber types. The nutrient supply to the basal cell layer occurs via the dermis.
In this basal cell layer there are specific cells for the recognition, marking, and neutralization of pathogenic microorganisms in case of injuries. In the epidermis/outer skin there are also the pigment-forming cells (melanocytes). Their product, the pigment melanin, gives the skin and hair their color tone. 5-10% is the cell proportion in the basal cell layer. With the amino acid L-tyrosine, the melanocytes can produce melanin. A deficiency thus has biological consequences when sunbathing intensively without prior biologically sensible adaptation!
2. Dermis (leather skin)
The tissue beneath the outer skin is referred to as the dermis (leather skin or corium). The dermis consists of various fibers such as collagen and elastin fibers, which ensure that the skin is stable and at the same time elastic. There are different types of fibers: short or long fibers, which in turn have specific properties. Because certain fiber types decrease with increasing age (usually from 30 years onwards), the skin becomes increasingly slack. Also, the firmness of the connection between the lowest epidermal layer, the basal cell layer, and the dermis is determined by these fiber types, which over time becomes looser and looser. In the leather skin, blood vessels and lymphatic vessels are also embedded, which serve the nutrient supply and the removal of metabolic products. The leather skin also harbors the so-called skin appendages, which partly belong to another germ layer and also react accordingly differently, e.g., hair follicles (ectoderm), sebaceous and sweat glands (old mesoderm) as well as numerous nerve fibers for tactile and vibration perception (ectoderm).
3. Subcutaneous fat tissue
The subcutaneous fat tissue (subcutis) consists of connective tissue and fat cells. It serves as cold protection and energy storage.