Corpus: Dermis

The term dermis or dermis is used to describe the collagen fibre-rich, connective tissue layer of skin that underlies the epidermis.

The term sclera is also used as a synonym for the sclera in the eye.

The dermis varies greatly in thickness depending on the body region. Histologically, the dermis is divided into two layers:

• Stratum papillare ("cone layer"). About 20% of the dermis, interlocked with the epidermis. It is named after the connective tissue papillae it contains. The loose connective tissue contains capillaries, lymph capillaries, nerve endings, connective tissue cells and Meissner's palpation bodies.
• Stratum reticulare ("reticular layer"). About 80% of the dermis, adjoins the subcutis. Consists largely of collagen bundles (predominantly collagen type I), which are linked together like a scissor lattice, giving the skin its tensile strength. Elastin fibres provide the dermis with restoring forces.

In contrast to the epidermis, the dermis contains blood vessels, hair follicles, nerves, sebaceous glands and sweat glands.

The arrangement of the connective tissue fibres in the dermis determines the course of the skin cleavage lines, which are clinically relevant during operations, for example.

The blood vessels of the dermis form two plexuses: the plexus profundus, which lies basally in the stratum reticulare, and the plexus superficialis, which is located in the stratum papillare and supplies the epidermis via diffusion through projections that extend into the papillae. In addition to supplying tissue, these blood vessels also have the function of thermoregulating the body.

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