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Figure 1
Early
development of the hair follicle and primitive hair shaft. (A) Initial state
of epidermal epithelium atop dermal mesenchyme. (B) Signal (probably from
mesenenchyme) initiates local proliferation of the basal keratinocytes (epidermal
stem cells) in the epidermis. (C) Proliferation of epidermal stem cells
results in the formation of the hair germ, which signals the dermal mesenchymal
cells to aggregate beneath it into a dermal papilla. (D) The papilla signals
the continued proliferation of the hair germ, making it into a hair peg
(or primitive hair shaft). The dermal papilla cells proliferate and tightly
aggregate. (E) The primitive hair shaft engulfs the dermal papilla and forms
the inner hair root directly above the papilla. (After Philpott and Paus,
1998.) |
