All About Hair
Buying or making the right hair care products is important but, before you do it’s also important to understand a little more about that stuff popping out of your head and the factors that influence its health.
What is hair?
Hair or fur, whatever term you choose to use, originates under your skin. (Maybe we should stick to the word “hair” when referring to us humans. It just doesn’t sound right to say, “Sweetheart, you have such lovely fur.”)
How does hair grow?
Hair originates in a tiny opening in your skin. Therein dwells the hair follicle. Within the hair follicle is the hair root and location from where the hair grows. When the hair leaves the follicle and emerges through the scalp, it is called the hair shaft. At the base of the hair root is the hair bulb, the location where new cells are formed and nourished.
Why doesn’t the hair on our arms and legs grow long like the hair on our head?
We have hair all over our bodies with the exception of the palms of our hands, the soles of our feet, our lips, and the back of our ears. Most of our hair is almost invisible vellus hair. That’s because it’s slightly different than the longer, thicker (terminal) hair that grows on our head, under our arms, and pubic area.
Vellus hair predominates during prepubescence, but with the hormone changes that come with puberty vellus hair is replaced by terminal hair under our arms and on our public area. Interestingly, when baldness occurs, the terminal hair is replaced by vellus hair.
What makes hair shiny?
Attached to the hair follicle are wee sebaceous (oil) glands. Sebaceous glands produce the oils that lubricate your skin and hair. (In case you’re interested, vellus hair is not connected to a sebaceous gland.) In humans, the scalp and face are the sites with the most sebaceous glands. The oil, sebum, produced by these glands is odorless, but can develop an odor due to bacterial action if it’s not washed off regularly.
As these new hair cells move up through the scalp, they become keratinized. This means they lose their nucleus (the heart of a cell) and fill with a fibrous protein. In other words, it’s become keratinized proteins and fiber and is no longer living. This new dead stuff streaming slowly out of your head is made up of three layers: an outer layer of keratin scales called the cuticle, a middle layer or cortex consisting of keratinized protein fibers, and a central core or medulla of round cells. (The central core is most commonly seen in thick hair. Thin hair and blond hair may be missing the medulla.)
What Makes Goose Bumps?
Attached to the hair follicle is a tiny muscle, the arrector pili. That muscle is responsible causes hair to stand on end or lay flat. When the muscle raises the hair, the result is a goose bump.
Dead things aren’t healthy
The term ‘healthy hair’ used by marketers of hair products is actually a misnomer. Unlike the hair follicle that spends its life producing new hair, the hair it grows is biologically inactive. That’s the reason you don’t scream in agony when you cut your hair, fingernails, and toenails. All of them are made up of keratin and are quite dead.
How does hair grow?
From the time hair starts to grow until it falls out is two to three years. Hair grows at a rate of about one centimeter a month. (Roughly 90% of the hair on your scalp will be in a growing phase) When it’s grown to its maximum length (the maximum length is normally genetically determined), it goes into a three to four month resting phase then falls out. About 10% of the hair on your scalp will be in the resting phase.
What is damaged hair?
Damaged hair is brittle or split on the ends. It could also be said that hair that is thinning is damaged, but this damage occurs at the follicle versus on the shaft or towards the ends.
What Causes damaged hair?
Split ends and course brittle hair is usually the result of:
- Excessive washing and blow drying
- Living in a dry climate
- Excessive hair treatments such as dyeing and perming.
Excessive hair loss is usually the result of:
- Stress (Note: you may not notice the hair loss for three or so months after an extremely stressful event. You have cortisol to thank for that.)
- Post surgery or after an illness (Normally, it will grow back.)
- Some medications including those used to treat hypothyroidism
- Reduced estrogen levels (women).
- Genetics (men and women)
- Extreme malnutrition – This can be due to lack of food or the lack of ability to properly digest food.
In future posts we will be discussing other aspects of healthy hair (yes, I mean at the follicle level) and ways to keep your hair shiny and beautiful. Stay tuned.
Now go have fun and relax.
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