Hair Follicles: The Complete Structure, Functions & Related Diseases

Your hair is your life’s biggest love and you cannot part with it, right? Each of your hair strands is produced by the hair follicles situated on the outermost layer of your scalp. This means, your hair health is directly related to your scalp health and hair follicles.

The average human has 100,000 hair follicles on the skin. Thus, your hair follicles deserve some spotlight when it comes to hair care. So, keep reading to understand the structure of your hair follicles, its functions and hair issues.

Highlights:

• What Is Hair Follicle?
• Hair Follicle Structure
• Hair Follicle Functions
• Hair Growth Cycle
• Diseases Associated With Hair Follicles

What Is Hair Follicle?

Hair follicles [1] are tiny holes or pores in your skin. Their main function is to grow hair. The scalp of your head too has hair follicles.

In biological terms, hair follicle looks like a tunnel-shaped structure situated in the epidermis (outer layer of the skin) [2]. Hair growth starts at the bottom of the hair follicle.

The root of your hair is made up of protein (keratin) [3] and derives its nutrition by blood from the blood vessels on the skin. The sebum or natural oil produced from sebaceous glands [4] near the hair follicles keeps the hair and scalp lubricated.

Hair Follicle Structure

Your hair is made of two parts - the hair follicle and the hair shaft. Hair follicle anchors or holds the hair into the scalp. It has the following parts [5]:

1. Bulb

The bulb is found at the root of your hair where the protein cells (keratin) grow to make hair.

2. Papilla

The papilla provides blood supply to the hair follicles for healthy hair.

3. Germinal Matrix

Germinal matrix is the region where the cells produce new hairs. This is located in the lower region of the hair follicle.

4. Bulge

Bulge is located in the middle of the hair follicle. It has stem cells that regenerate hair follicles, sebaceous glands and epidermis. Bulge also has arrector pili, the muscle tissue that makes your hair stand on the ends when you experience goosebumps.

Hair Follicle Functions

Besides growing hair, hair follicles play an important role in deciding how your hair should look.

The shape of your follicle is related to the type of your hair. Circular hair follicles make straight hair while oval follicles make curlier hair.

Another function of hair follicle is giving color to your hair. Hair, like your skin, gets its color from a pigment called melanin [6]. This melanin is stored in the hair follicles. There are two types of melanin - eumelanin and pheomelanin.

• If you have lots of melanin you will have balck hair.
• If the eumelanin is moderate, your hair is brown.
• If you have very little melanin, your hair is blonde.
• If you have pheomelanin, your hair is red.

The ability of hair follicles to produce melanin decreases as you age and as a result, you will see grey or white hair strands.

Normally, hair grows at the rate of half an inch every month. This rate is impacted by your

• Age
• Hair type
• Overall health

Normally, if you pull out hair from a hair follicle, it has the capacity to grow back new hair. In certain medical conditions, hair follicles can no longer grow hair and lead to bald spots or patches.

Hair Growth Cycle

Hair from the hair follicle grows to the surface in cycles.

1. Anagen (growth phase)

This is the phase that lasts between 3-7 years. The hair begins to grow from the root.

2. Categen (transitional phase)

In this phase, growth slows down and the follicle shrinks. This may last up to 2-4 months.

3. Telogen (resting phase)

The old hair falls out and paves the way for new hair to grow back from the roots all over again. This phase may last up to 3-4 months.

Not all the follicles on your scalp are in the same phase at any given time. Different follicles go through the three different growth stages.

In a healthy human, 90% of your hair follicles are in the growth phase or anagen phase. A healthy person can lose about 100 strands a day.

Diseases Associated With Hair Follicles

1. Androgenetic Alopecia

Androgenetic alopecia [7] or male pattern baldness is a condition that impacts the growth cycles of hair follicles on the scalp. The hair cycle is slowed down and comes to a halt. The follicles are not able to produce hair anymore. This can affect women too and is called female pattern baldness when it presents itself in women.

2. Alopecia Areata

Alopecia areata [8] is an autoimmune disorder, meaning the body's immune system attacks its own hair follicles. This results in hair that falls out in clumps. Steroidal injections and topical creams slow down hair loss in this condition, but there is no cure to stop the hair fall completely. Alopecia can sometimes lead to alopecia universalis - total hair loss from all over the body.

3. Folliculitis

Folliculitis [9] is an inflammation of the hair follicles. Folliculitis can affect the scalp, armpits, face, arms or legs. Folliculitis or hair follicle infection manifests as small red, yellow or white bumps or rashes and may contain pus. It is caused by a staph infection (bacterial infection).

4. Telogen Effluvium

Telogen effluvium [10] is a temporary form of hair loss. Post traumatic stress can cause the follicles to go into telogen or resting phase prematurely. Childbirth, surgery, illness, physical or mental trauma can trigger telogen effluvium.

Note:

Consult your dermatologist if you notice any sudden and unusual hair shedding or inflammation on the scalp.

Wrapping Up

Hair follicles produce hair in three growth phases. They also determine the type and color of your hair. Damaged hair follicles can cause inflammation or hair loss. Thus, understanding the science behind your hair follicles and opting for the right hair care regimen is crucial if you want healthy hair.

Begin By Knowing Your Skin