Dermis

The dermal mesenchyme arises from different sources. In the region of the trunk and the limbs, it comes mainly from the somatopleuric mesenchyme (parietal mesoderm); in the region of the back, it comes mainly from dermatomes of the somites. In the region of the head and neck, mesectoderm from the neural crest is an additional component. During the early stages of development, the connective tissue of the dermis is still loosely spread and free from blood vessels. It is assumed that the vessels arise from angiogenic mesenchymal cells in situ. After month 4, dermis and epidermis become more interconnected. Dermal papillae interdigitate with the epidermis.