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Hair shaft

Hair Shaft
In the hair structure diagram above, you can see that the shaft has three layers: the cuticle (outer layer), cortex (middle layer) and medulla (inner layer).
The medulla is a honeycomb keratin structure with air spaces inside.
   The cortex gives flexibility and tensile (stretching) strength to hair and contains melanin granules, which give hair its color (blond in the diagram above). The cortex is made from tiny fibers of keratin running parallel to each other along the length of the hair shaft (as shown in the photo of the split hair end above).
The cuticle is made from 6 to 11 layers of overlapping semi-transparent keratin scales (which make the hair waterproof and allow it to be stretched). Someone with thick, course hair will have more overlapping layers of cuticles than someone with fine hair. You can see the cuticle layers in the photo above. And in the diagram, you can count 6 cuticle layers.
Take a Closer Look
Beneath the skin of keratin
As already stated, hair cells are mostly made from keratin (up to 95%). And, like all proteins, keratin is made from amino acids. Sixteen amino acids form keratin, with cysteine having the highest concentration. And cysteine is one of just two amino acids that have a high sulfur
content (the other being methionine).
The significance of all this is that the mineral sulfur is known to be beneficial for hair growth. Clearly then, sulfur is a very important component of hair structure.
Different type of hair – Same type of hair structure
There are three types of hair – lanugo, vellus and terminal.
All of them share a similar basic hair structure, but each plays a different role in the body:
Lanugo hair starts growing when you’re still in the womb, but falls out either just before or just after birth. (So, in other words, you might experience hair loss before you’ve even been born!)
After your lanugo hair falls out, it gets replaced by vellus hair – this is the tiny, near invisible hair that covers your body.
However, a lot of vellus hair turns into terminal hair (which includes eyebrows, eyelashes and scalp hair). And male hormones (androgens) also stimulate vellus hair to “mature” into facial hair, body hair and pubic hair.
Paradoxically, the very same androgens associated with hair
growth , have also been associated with hair loss (androgenetic alopecia). These include testosterone and dihydrotestosterone (DHT). So, let’s take a look at where within the hair follicle these androgens act…
Which hair structures are connected to hair loss?
People with hair loss tend to have higher levels of 5-alpha reductase and androgen receptor sites in the hair follicles within the hair loss region of their scalp. 5-alpha reductase is an enzyme that converts testosterone into DHT. And androgen receptor sites are essentially attachment points for androgens (especially DHT).
In the hair follicles, 5-alpha reductase is found within the
sebaceous glands and outer root sheath, and androgen receptor sites are found in dermal papilla cells (please refer back to the color-coded
hair follicle diagram).
As you can see, these two important components of the hair loss process seem to be somewhat scattered across the various structures of the hair follicle. So, perhaps not surprisingly then, this only adds to the complexity this puzzling type of hair loss presents.
However, it’s a puzzle that has now been solved – take a look at the Skull Expansion section to find out.
So, now you know all about the various structures which form the hair follicle and the hair shaft, find out on the next page how they all interact to create the hair on your head over and over again throughout life.
This is page 1 of 3.
Read next page? Hair Growth Cycle.
Leave Hair Structure – Return to Articles Index.
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