File:Hair follicle StemBook.jpg

English: The hair follicle growth is stimulated by the dermal papilla (DP) signals, activating the bulge stem cells (Bu) to form the distinct lineages of the hair follicle (HF). Several concentric layers composed the HF. The external and basal layer, called outer root sheath (ORS) maintains contact with the basal layer of the inter-follicular epidermis (IFE). At the base of the HF, the matrix cells (Mx) represent the highly proliferative cells, which differentiate in concentric rings that give rise to the Hair shaft (HS) and its channel the inner root sheath (IRS) and the companion layer. The HF contains also the sebaceous gland (SG), which produces the waterproof sebum. In the left panel, skin was co-stained for the basal cells using the anti-keratin14 antibody (red) and for the bulge SC using the anti–CD34 antibody (green). In the right panel, skin was co-stained for the basal cells using the anti-β4 antibody (white), for the Mx cells using the anti–KI67 antibody (red) and for the HS precursors using the anti-AE13 antibody (green). Nuclei were marked using DAPI staining. Abbreviations used: Bu: bulge stem cells, Der: dermis, DP: dermal papilla, IFE: inter-follicular epidermis, IRS: inner root sheath, HF: hair follicle, HG: hair germ, HS: hair shaft, IRS: inner root sheath, Mx: matrix cells, ORS: outer root sheath, SG: sebaceous gland.