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 third wave of hair formaiton starts at E18.5, continues till birth and generates zigzag hair. The first wave of hair formation forms the guard hair and the second produces the awl hair.
Multiple AncestorsSingle AncestorNo DescendantsDevelops fromPart of Parent