Embryogenesis of the dermis in human skin.

The process of human dermal development has been examined from the stage of the embryonic mesenchymal dermis (5-8 weeks of gestation) through the formation of the fibrous dermal connective (end of the first trimester), and during the growth of the fetal dermis (second and third trimesters) until birth. The elaboration of dermal organization and the overall increase in dermal thickness, largely consequences of extracellular, fibrous matrix accumulation, parallel the development and growth of the fetus as a whole. Although the mechanisms that determine the formation of the connective tissue architecture are not fully understood, the structural, histochemical, and biochemical changes that occur throughout development suggest processes that may be important in human dermal embryogenesis.