Skin

Structure of the skin

The skin (cutis), with an area of about 2 m2 and accounting for 15% of body weight, it is one of the largest organs in humans. It consists of the epidermis (upper skin) and the dermis (leather skin) underneath. The outermost layer, the epidermis, is a keratinized, multilayered squamous epithelium without blood vessels. The most important cell type is keratinocytes, which form keratin, a water-insoluble fibrous protein. The epidermis also contains the pigment cells (melanocytes) and immune cells. Its outermost layer, the stratum corneum, consists of dead horny cells. The epidermis is constantly renewing itself from the bottom up.

  • Epidermis
  • Dermis

The dermis is perfused and consists of connective tissue with elastic collagen fibers. The most important cell type are the fibroblasts. The dermis contains nerves and receptors and represents the origin of hair and glands. Under the dermis lies the subcutis (hypodermis), which is anatomically not counted as skin and contains fatty tissue. The cutis and subcutis together form the skin cover. Important skin appendages include the hair, nails, eccrine sweat glands, apocrine scent glands, and sebaceous glands.

Functions of the skin

The skin performs several important functions for the body.

  • It provides a barrier against harmful influences and against infections. It protects against physical, chemical, thermal and biological stimuli.
  • The skin has water-repellent properties. On the one hand, it protects against water loss from the inside and on the other hand ensures that no water from the outside penetrates into the tissue.
  • The skin is important for thermoregulation. It prevents heat loss and with sweating hyperthermia.
  • The skin is a sensory organ that senses touch, pressure, pain, heat and cold.
  • The skin also has a metabolic function. It synthesizes vitamin D in the lower layers of the epidermis, in the stratum basale and stratum spinosum.
  • The skin has an important communication function and is important for the external appearance and physical attractiveness.
  • Finally, the skin can regenerate itself and heal wounds.