Skin, which is the main organ of touch, covers our entire body. It is a flexible, thick and tough membrane that enables us to experience a vast amount of physical sensations, from the pain that comes with a strong blow to the motion of our hair when it’s windy.
It is also responsible for perceiving cold and heat. In adults, the surface of the skin can reach up to 1.5 to 2 m2. On average, it weighs nearly five kilos. Its color depends on a pigment called melamine. Skin is made up of three layers: hypodermis, dermis and epidermis.
– Hypodermis is the innermost layer. It is a coat of fatty tissue that is formed by adipose cells. It is one of the largest and most important energy sources of the body.
– Dermis is the intermediate layer of the skin and it is responsible for the skin’s flexibility and resistance. It is split into two parts: papillary or superficial dermis (rich in cells and blood vessels) and reticular or middle dermis (rich in collagen and elastic fibers).
– Epidermis is the outermost and thinnest layer of the skin. It contains a high percentage of keratinocytes, cells that produce a protein called keratin. Keratinocytes form four strata (layers); the following are said layers from outermost to innermost: stratum corneum, stratum granulosum, stratum spinosum (or Malpighian) and the stratum basale or germinative layer. The epidermis also has Langerhans and Merkel cells.
