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Fig. 1. Adult human skin is a layered organ consisting of an epidermis that is attached to a dermis by an elaborate connective tissue structure, the basement membrane (BM). The basal surface of the epidermis is indented by dermal and vascular components called dermal papillae (*). The dermis is divided into two functional layers, the papillary dermis and reticular dermis. These two layers are separated by a vascular plexus, the rete subpapillare. This plexus is fed by another vascular plexus, the rete cutaneum, located at the base of the reticular dermis. Skin also contains hair follicles (HF) and glands (not shown). Two distinct populations of dermal fibroblasts have been cultured from the interfollicular dermis, the region between hair follicles. Papillary fibroblasts (PF) are cultured from skin dermatomed at a depth of 0.3 mm and reticular fibroblasts (RF) are cultured from skin located at a depth below 0.7 mm. Hair follicle fibroblasts are obtained by carefully plucking or dissecting hairs from the skin and then placing these hairs or segments of these hair follicles onto surfaces of plastic culture dishes. Hair follicles contain two subsets of cells: the follicular sheath cells and dermal papilla cells.
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