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Structure and Function of Hair :-
Hair is mostly made of a protein called keratin, the same stuff found in our skin and nails.
This keratin is very tough, which makes our hair strong and durable.
Each hair grows out of a tiny hole in our skin, called a follicle.
The part of the hair that’s visible, is called the hair shaft; and the part inside the skin, is called the hair root.

If we take a closer look at a hair’s cross-section, we can find - it has three layers.
The outermost layer is called the cuticle, made up of flat cells that overlap like roof tiles.
This layer protects the inner parts of the hair.
Beneath the cuticle - is the cortex.
This is the part made up of keratin and responsible for the strength of the hair.

The cortex also contains melanin, the pigment responsible for the color of the hair.
There are two types of melanin: eumelanin and pheomelanin.
If hair gets a lot of eumelanin and very less pheomelanin, hair becomes dark black.
Less eumelanin makes it brown.
When pheomelanin is dominant, hair turns red or blond.
More pheomelanin makes hair red, while less of it makes hair blond.

Deeper inside the cortex, there’s another layer called the medulla.
This part contains air spaces and soft keratin, making hair lighter and more flexible.
Medulla is only found in thicker hair, like the hair on our head, beard, and armpits - these are called terminal hairs.
The thin, soft hair on the rest of our body, called vellus hair, doesn’t have a medulla.

Above the skin is what we see, but the real action happens under the surface of the skin and inside the follicle.
At the bottom of the follicle is the bulb, where new hair cells are made.
The bulb has a little bump called the papilla, which contains blood vessels that supply nutrients to the growing hair.

Attached to the follicle is a gland, known as the sebaceous gland, that produces an oily substance called sebum.
Sebum keeps our hair and scalp moisturized and soft.

There is also a tiny muscle attached to the follicle, called the Arrector pili.
Ever noticed our hair standing up when we are scared or cold?
That’s this muscle in action.
When this muscle contracts, we get goosebumps.


The shape of the follicle determines the texture of our hair.
If it’s round, our hair becomes straight.
If it’s slightly oval, our hair becomes wavy.
And if it is flat, we have curly hair.

The health of our follicle also affects how strong and fast our hair grows, how much hair we have, and how much of it falls out.

But it is also true that hair doesn’t grow forever, and some hair naturally falls out, no matter how healthy the follicle is.
To understand this, we need to talk about the hair growth cycle.

This growth cycle has three phases.
The first phase is called Anagen, when our hair is actively growing.
This can last anywhere from 2 to 6 years.
Then comes Catagen, where the follicle shrinks, and hair stops growing.
This phase lasts only for a few weeks.
Finally, there’s the Telogen phase, when the hair falls out.
If the follicle remains healthy, new hair starts growing from there.

We all hope that new hair grows in place of the fallen ones because healthy hair - especially on the head - makes our face look more attractive.
But hair isn’t just for looks; it provides us with plenty of protection and also keeps us warm.


Hair protects our scalp from the sun’s harmful rays and acts as a shock absorber in minor injuries.
Eyebrows keep sweat from dripping into our eyes.
Nasal hair traps dust and bugs, keeping them from entering our lungs.

Even the air trapped between hair strands helps insulate us from the cold.
That is why we feel cold after shaving our head or beard.



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#hairgrowth
#science