The taxonomy of the human hair is quite a bit different than the hair in most other mammals and has a distinct pattern of growth that varies also from other species.
During the fetal stage of development, fine downy hairs are produced in the skin. These hairs, known as lanugo* are the first hairs present at birth, but are soon replaced by vellus hairs post-partum. The only areas on the normal human infant that have any terminal or anagen hairs at birth are the scalp (capilli), eyebrows (supercilia) and the eyelashes (cilia). The rest of the body’s hairs are vellus within a relatively brief period of time. This condition will remain stable until the onset of puberty.
There are two ways that vellus growth can be stimulated. The first is by an increase of blood supply to an area. The second is by hormonal stimulation.
Remember that most of the body’s vellus hairs begin from lobes on the sebaceous gland. Certain things that increase the blood supply to an area of the body will cause some vellus hairs to become darker, thicker and longer. They will also begin to develop a bulb. However, at this time, they have not become terminal hairs and may be designated as “accelerated vellus growth.”
To quote Hinkel and Lind from Electrolysis, Thermolysis and The Blend, pg.3, 3rd par.,
If a vellus (or lanugo)hair is already growing from, say, the lobe of a sebaceous (oil)gland, an increase of blood supply to the immediate area greatly enhances it’s growth. As if the hair were being “fertilized” by the influx of this unaccustomed nourishment, it tends to grow deeper and coarser, becoming an “accelerated” lanugo (read vellus*)hair. (i.e., one which is just beginning to acquire a builb and take on pigmentation; it is not yet a “terminal hair”)
Additionally, at the onset of puberty, androgen begins to be produced at levels sufficent to stimulate hair growth when this substance reaches the target organs known as the sebaceous glands, where it is converted into dihydrotestosterone (DHT). DHT is a powerful hair growth stimulent. This and other substances, such as cortical steroids, stimulate germ cells near the sebaceous glands into lanugo (read vellus) hair growth.
These hair-germ cells (as Montagna refers to them) need only to be “turned on” by the chemical action of the hormone. They then begin to multiply and divide, creating a lanugo* hair structure which may continue to accelerate in growth. Thus the action of certain hormones is capable of eventually bringing about a coarse, pigmented hair where no hair at all had existed.
(Page 3, 4th par.)
The main thing here is that every hair will exist as a vellus hair at some point in it’s development. As it grows towards the terminal hair stage there will be a point where it will have the beginnings of a bulb, but will not have developed or deepened to terminal stage growth. At this stage, the hairs may be considered “accelerated vellus” hairs and are shallow, smaller and very easily treated.
I do agree that accelerated vellus hairs do have the ability to eventually develop into terminal growth (anagen) hairs. Sometimes this happens quite quickly. One of the things that I look for when treating the female upper lip, chin and cheeks are hairs that are in the “accelerated vellus” stage. If I can spot these, I will eliminate them when they are still small and shallow to prevent them from reaching terminal growth.
This can be done very quickly at relatively low power settings - with a much lower discomfort level. As vellus hairs do generate from lobes of the sebaceous glands, they are very susceptable to hormonal stimulation causing them to progress to anagen growth. This is particularly true for post-menopausal and women who have undergone hysterectomy.
One other note that I’ll include here: Anagen is the initial stage of terminal hair growth. Once a hair reaches anagen growth, it has now gone into the realm of the terminal hair and will now go into the anagen, catagen, telogen cycle of repetative growth that is the reason that we are all here. One other thing of note though. Not all hormonally triggered hairs develop from the vellus hairs. Some are produced by the hormonal influence of small clusters of undifferentiated clusters of hair germ cells in the skin. These cell clusters, when hormonally triggered, develop into terminal hairs. This is the reason that many of us will eventually require occaisional-clean ups to get the hairs that have “grown where no hair has grown before!” (groan!) As another pro here has indicated, various stages of life place other complications on our bodies and what happens to us. Certain medications, that many of us need at later life stages, sometimes trigger new hair growth by effecting our endocrine balances. These hairs are not regrowth, but a whole new set of hairs that have been developed by the body. Time marches on…All over our bodies!
*Taxonomically speaking the term “lanugo hair” is now taken to mean the fine hairs produced in the skin during the fetal stages of development. More modern information states that the lanugo hairs become vellus shortly after birth.
I hope this clarifies what I was talking about.
Joanie <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
P.S. I could have stated this a lot simpler, however I felt it was necessary to expand on the topic to allow the average consumer to understand what you were asking me and what my response meant. Before I studied electrology, I never knew that hair could be so complicated! (Forgive me! I’m a blonde! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />)