A vellus ( thin & light pigmented) hair follicle goes down to the deep dermis, however a terminal (thick & pigmented) hair follicle goes deeper, until the subcutaneous tissue. Terminal hairs are seen on the scalp, eyebrows since birth and on beard, axilla and genital areas after puberty. A good scalp biopsy should include terminal hair bulbs and usually is 0.8 to 1cm deep.
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