Different Hairs and Their Growths

I posed a question upon a peer who did not envisage in her wildest dreams the question asked to ever be asked out loud or in her direction, with the asker, myself, awaiting a legitimate response. I asked her if she thought there was anyone on this planet with armpit hair long enough to plait.

And that sparked a new journey of inquiry, one of which I am delighted to partake in because I imagine, like that unsuspecting peer, a scarce amount of people would step out of the box every now and again to raise questions like this without holding back. Surely enough, the entire lecture theatre's attention was brought to me and judgements were made, but I can very well assume that nobody knows the answer, which is why they all laughed and gave me weird looks instead of explaining why hair on different areas of our bodies stop growing whilst others continue, for example, our pubic hair and the hair on our head. What stops our pubes from growing down to our knees? What is it that drives the hair on our heads to continue growing?

Hair growth takes place in three stages, the first being Anagen, the second Catagen, and the third Telogen. Through each phase, the length of the hair within it is determined, and hairs may depending on their moods switch phases. Our hairs do not have moods, per se, but it is easier to comprehend those stages if they were contrasted or aligned with human characteristics, which we all understand the most. These three stages, phases or cycles, depending on which synonym you prefer, promote the hair growth of 1.25 centimetres a month, which amounts to about 15 centimetres per year.

The first stage, Anagen, is the growth phase. It can last from two to six years. Hair growth in this stage depends on genetics, so in my case, because of my Lebanese heritage, I am supposing that my hairs last in this stage for about seven years, defeating the estimated length of the phase because Lebanese hair is everywhere and it simply does not stop growing. And while the hair is in the Anagen phase, it will grow faster and longer, so that fact simply aligns with the rapidity of Middle-Eastern hair growth. Trust me, I am an advocate for it. At any given time, 85% of the hairs on our heads are in the Anagen phase. That explains why the hair on our heads do not stop growing, apart from that stubborn 15% which are more likely to frizz and stand during important photoshoots. 

In the second stage, the phase of the Anagen is stopped by the sending of signals to certain hairs, and the Catagen stage begins, wherein the hair follicle renews itself - just when you did not think your hair would become any stronger, you were wrong - check yourself before you Catagen yourself. During this period of two weeks, the hair follicle then shrinks and cuts its long hair strand away from its nourishing blood supply. The follicles going through Catagen simply loathe being overshadowed by the big, buff Anagen's hairs, so in intimidation, in this fight or flee situation, they do what any wild Pok'emon that you really need on your Pok'edex do - flee; they send off their beautiful locks of hair and stay immobile in your scalp. They are then what Katy Perry sings about, 'the [hairs] that got away'.

These intimidated follicles then go through their final phases, the Telogen phase. During this phase, the follicles lay dormant like stubborn volcanos, for a period of one to four months - Middle-Easterners experience this for a maximum of one month, because our hairs enjoy moving on and strengthening. Those obstinate 15% of hairs in the Anagen phase are going through the Telogen phase - temporarily anchored in place, they choose to wear Harry Potter's invisibility cloak. When these hairs wish to be seen again, they break free like Queen and shed, soon after growing again into the Anagen phase.

But that does not really explain the varied lengths of varied hairs, does it? Well, there are two types of hair other than the hair on our heads - the Vellus, and the Androgenic. The Vellus hairs are those which appear to be blonde, but are the same colour as any hair on Middle-Easterners. These prepubertal hairs are located anywhere except for on the palms of your hands, on lips, on the back of your ears, the soles of your feet, some external genital areas, and on your navel or scar tissues. Some of these go on to develop into Androgenic hairs or terminal hairs once puberty is reached, wherein hair darkens and thickens. 

Vellus hairs, their name originating from the Latin word fleece, grow from 2-4 centimetres long, and do not exceed that length. They insulate and cool our bodies, like feathers birds. They assist us in perspiring, which is not really any assistance at all especially during meetings or important interviews. Androgenic hairs, on the other hand, grow during puberty and thicken depending on gender, rather, hormones - because males have more androgen, hence the name, in their bodies, they have much more Androgenic hair than females. The image below shows the general distribution of Androgenic hairs in males and females:

source

The following is the period of growth in the three stages for head hairs and other hairs:

Head Hair

Anagen: 2-6 years

Catagen: 2-3 weeks

Telogen: 3 months

Eyebrows and other hairs:

Anagen: 4-7 months

Catagen: 3-4 weeks

Telogen: 9 months

From the observation of the period of growth table above, it becomes clear to us that the reason as to why the hairs on other parts of our bodies do not grow as long as the hair on our heads is because during the phases that they go through, they take less time, thus there is less time for growth. In the Anagen phase, the hair on your head grows from two to six years, whereas hair everywhere else only has four to seven months of growing time before becoming dormant and stubborn. In the Anagen phase, hair grows 1 centimetre every 28 days, which means that the hairs on our head grow from 26 to 78 centimetres before they become dormant, and hair everywhere else grows only 4 to 7 centimetres before they become dormant.

Had somebody explained this to my not-so-seriously-posed-and-quite-satirically-delivered question, then I would have not gone through this strenuous effort to give you an explanation about this inquiry. You are quite welcome. Consider this informative satire. And to answer my question, no, there are no such humans which can grow armpit hairs long enough to be able to plait them.






References

Hair Follicles:
http://en.wikipedia.org/wiki/Hair_follicle

Androgenic Hair:
http://en.wikipedia.org/wiki/Androgenic_hair

Vellus Hair:
http://en.wikipedia.org/wiki/Vellus_hair