What’s New in Hair Biology?
Did you learn this in beauty school? Have you heard of FGF5? The hair growth cycle? Read on to learn about the formation, life and death of a single hair….the start of being a Hair Biologist…..
Hair follicles are formed in the womb and the number of follicles is fixed at that time, we cannot grow more. The follicles form as a part of the epidermis, the outer layer of skin.
The future follicles in the epidermis burrow down into the dermis, the deep layer of skin, to form hollows or pockets which will house the hair itself.
At the base of each follicle a group of cells is formed, called the germinal matrix. This group of cells is nourished by the dermal papilla, a cluster of blood vessels at the base of the follicle bringing nutrients to the germinal matrix. In effect, each follicle functions as a single unit, independently of the others, with its own ‘stem’ cells. The cells in the germinal matrix constantly divide when hair is actively growing, pushing up the follicle and forming the hair. As the cells push up, they pick up pigment and differentiate from each other to form the 3 layers of hair, gradually flattening and hardening as they reach the scalp surface, forming the visible hair. We call this process keratinization because it describes the formation of keratin, the hard, protective protein that hair is made of. Hair above the scalp surface is fully keratinized or completely hardened, fully formed hair keratin with a cuticle – outer layer, cortex – inside layer, and sometimes a medulla – airspaces in the center.
Hair follicles are present everywhere on the body except the lips, eyelids, soles and palms. Scalp hair is called terminal hair, it is thick in diameter; the finer, shorter hair on the body is called vellus hair.
Healthy hair grows in 3 distinct stages, we call this the hair growth cycle.
Period of active growth, called anagen. The cells in the germinal matrix are being nourished by the dermal papilla and constantly divide, pushing up the follicle, forming the hair shaft
Lasts for 2-7 years, growing constantly, around 1cm or half an inch each month. Hair that grows for 2 years can be 24cm long, hair that grows for 7 years can be 84 cms long.
Transition stage, called catagen. Dermal papilla loses contact with the germinal matrix as the follicle shrinks slightly, pulling away from the blood supply, so the cells here stop dividing, and hair stops growing actively. Hair stays in the follicle but will not get any longer. The root of the hair rounds, forming a club hair, separating from the base of the follicle and getting ready to fall.
Lasts for around 2 weeks.
Resting/Dormant stage, called telogen.
The hair follicle pulls away from the dermal papilla and shrinks up, all contact is lost. Hair falls out and follicle rests.
Lasts around 2 months.
At the end of telogen, the follicle lengthens to make contact with the dermal papilla, regenerating the germinal matrix and restarting the anagen phase.
What regulates the hair growth cycle?
Here is the fun stuff, the new stuff, the stuff that we didn’t know before, the recently discovered stuff……
Recently discovered FGF5 is a protein made in the scalp. It has one sole function; it pushes the hair from anagen (active growth) into catagen (transition)
Soooooo, FGF5 stops hair from growing. That’s right, FGF5 stops hair from actively growing. In healthy hair and scalp, not a problem as otherwise hair would continuously grow and never fall out (perhaps with strange consequences?) However, as we age, or suffer stress, illness, hormone imbalances, the amount of FGF5 can build up, forcing more of the hair to stop growing. The result is increased hair fall, and potentially thinning hair, receding hairline, wider parting, thinner ponytails….all the things we see in our customers.
So now we understand how hair grows, and what is responsible for increased hair fall. And that is the start of being a Hair Biologist.
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