Hair growth begins in
the follicle and the average person should be able to grow about 4-7 inches1
a year regardless if it is straight or curly, healthy or unhealthy, coarse or
fine. The follicle has several layers each designed to assist and protect the hair
strand as it grows out of the skin. Each follicle is also connected to a
sebaceous gland secreting sebum (an oily secretion) onto the surface of the
skin. The oil from this gland is all our scalp requires to stay moisturised and
does NOT need additional help. There is no need to grease your scalp, NO NEED!!
(My poor head! All throughout my life I was always told to grease my scalp, my
follicles were probably suffocating!). The base of the follicle is also known
as the hair bulb and is found in the dermis (the second layer of your skin).
Here the follicle obtains nourishment from the blood vessels and nerves in the
dermal papilla – the commander of the scalp. The dermal papilla controls the
scalp and organizes when, how quickly and how thickly your hair grows.
Hair growth occurs in
three circular phases: anagen, catagen and telogen.
Anagen - the growth period
- can last anywhere from 1-10 years2 (so the average head of hair can
potentially grow 4-70 (!) inches in a given growth period) but the average
length is about 3 years. During anagen, keratinocytes in the follicle produce
keratin to make the hair shaft. As it is the longest period in the cycle the
majority (90%) of your follicles are in the anagen phase right now.
The remaining 10% are in either the catagen phase (the transition period) or the telogen phase (the rest phase). Catagen lasts about three weeks2 and in this phase the hair is prevented from growing or producing melanin (which is why the bulb is white). The follicles shrink and the dermal papilla begins to break down in preparation for telogen. Telogen takes about three months, here the hair pretty much just waits there until stimulated to undergo exogen (shedding).
After about ten growth
cycles our ability to pigment our hair worsens and we begin to develop grey
hairs1 (this also happens during periods of stress, which is why
during or after exams you may find random greys1), if you have a shorter
growth cycle you also may discover yourself going grey earlier! More bad news:
less than half of women and 2% (!!!!) of men go through life with a full head
of hair3. So the lesson is, if you think your male friend going bald
is hilarious right now there’s a 1 in 2 chance that’ll be you in the future
(almost 100% if you’re a boy reading this)! :D
Maz xx
References
1 Krause, K; Foitzik, K (2006). Biology of the Hair Follicle: The
Basics. Seminars in Cutaneous Medicine and Surgery, Volume 25, Issue 1.
2.
Bernard A.
Bruno (2003). Hair Shape of Curly Hair. Journal
of the American Academy of Dermatology, Volume 48, S120-6
3.
Lai-Cheong,
J.E; McGrath, J.A (2009). Structure and Function of Skin, Hair and Nails. Medicine, Volume 37, Issue 5
Images taken from The Medical Dictionary & Stylecraze PS. Happy Independence Day to Ghana! xx
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