Dermal condensates are enclosed by cells of the inward growing epithelial placode. Reciprocal signaling between these two cell types leads to formation of mesenchyme-derived dermal papilla cells inside the epithelial envelope approximately at E16.5. Dermal papilla cells function as a signaling center during initial hair formation in the embryo, as well as during the hair cycle in adult. These cells transmit signals to the surrounding epithelial cells to continue proliferating and to differentiate into various cell types of the growing hair shaft.
The first wave of hair formation starts at E14.5 and forms the guard hair. The second wave of hair formation occurs at E16-E17 and produces the awl hair. The last, third wave, starts at E18.5 and continues till birth and generates zigzag hair.
Multiple AncestorsSingle AncestorNo DescendantsDevelops fromPart of Parent