Human hair follicles produce hairshafts of various types:
I) Lanugo hairs (of the foetus) are usually shed during the 7th month of foetal life following primary folliculo-genesis (the development of primary hair follicles which usually remain inactive until the neo-natal period).
2) Vellus hairs are soft, non-pigmented that rarely exceed a length of 2cm due to the short anagen phase of cyclic follicular activity.
3) Terminal hairs are coarser, pigmented or non-pigmented, exist on the scalp and gain length (dependant upon ethnicity) at a rate of 0.5cm – 1.7cm per 30 day month during a cyclical life of up to 10 years. In females this may not necessarily apply during pregnancy and the neonatal period.
Hybrid hair types exist.
In ‘Accelerated Vellus Syndrome’ the anagen phase of cyclic follicular activity is extended. This results in hairs gaining greater length. These hairs retain their colourless downy vellus characteristics.
Causes: Stimulation believed to be associated with certain drugs or endocrine changes, viz: post menopausal women and trans-gender (female > male) individuals.
© 2003 Claire Stevens FTTS