The normal hairy scalp has a rich blood supply which is commensurate with the tissue needs for growth and differentiation. The blood supply to the scalp does not seem to be a primary factor in the specific growth potential of the hair. It is probable that this growth potential is determined mainly by hereditary factors which control the size of the follicle, by the response of the follicle to growth hormones, and by its genetically oriented response to androgenic hormones. There is some evidence which indicates a decrease in the rate of hair growth in old age. The pattern of the blood vessels in the human scalp is a complicated maze; the greatest concentration of vessels seems to be at points of greatest metabolic activity, and the overall arrangement of vessels is in an interconnecting candelabra effect rather than in specific plexuses.
CORMIA FE. Vasculature of the Normal Scalp. Arch Dermatol. 1963;88(6):692–701. doi:10.1001/archderm.1963.01590240016004
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