Prenatal Hair Development: Implications for Drug Exposure Determination

The document discussed the development of hair follicles during prenatal stages, highlighting the interactions between ectodermal and mesodermal layers. Hair follicle development began around the 8th week with the formation of placodes, and by the 10th week, initial hair production started. By the 20th week, the entire scalp was covered with anagen phase hair. The first hair cycle concluded with catagen/telogen phases between the 24th and 28th weeks. The study emphasized that scalp hair fibers present at birth reflected metabolic activity occurring after the 28th week of prenatal development.