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Hair facts

Information about hair structure, hair shaft, functions hair, hair growth, hair growth cycle scalp, hair types, hair colour and hairy visitors.





Hair structure

Medically speaking your body hair contains dead cells. That's why it doesn't hurt when someone cuts your hair! Hair, fingernails and toenails are dead epidermal cells.

The human hair is divided in the hair shaft and the hair root. The hair root thickens at the end to become the bulbus. The hair shaft is the only visible part that grows above the skin surface.

Goose bumps are created when tiny muscles at the base of each hair contract and lift the hair in the follicle up in response to cold or fear.

The terminal part of the hair follicle seated within the skin is called a hair bulb.  Special cells in the hair bulb produce the pigment that colors the hair (melanin). As the developing hair moves upwards in the follicle the melanin is carried upwards in the inner part of the hair.

There are also some glands adjacent to the hair follicles. The most important one of these glands is the sebaceous gland, which produces and secretes sebum. The sebum allows the hair to slide through the scalp and protects the hair from the elements.

The part of the hair that is embedded in a hair follicle is called a hair root. At the heart of each hair follicle lies the dermal papilla. The lower portion of the follicle has an expanded shape and is called the follicle bulb where there is an area of actively dividing cells called the hair matrix. This is the source of hair production. The follicle and the hair produces continue through repeated cycles of growth and rest.




The hair shaft is made up of keratin in three layers

Every hair has basically two parts: the hair follicle and the hair shaft. The hair follicle is where the hair grows from (and you will not be able to see). It is alive and flowing with tiny blood vessels.

The hair shaft is the part you can see and is made of dead cells. The hair shaft is made of protein cells called keratin in three layers: the cuticle, the cortex (outer layer) and sometimes the medulla (inner layer).

The cuticle protects the cortex from damage and is responsable for your bad hair day.

The cortex gives the hairs its form, colour and body. The cortex can be slightly modified by dyeing, bleaching, perming and straightening.

When the cuticle and the cortex get damaged hair problems like split-ends arise.

There are pigment cells that are distributed throughout the cortex and medulla giving the hair it's characteristic color.

 

Functions hair     

Besides physical functions hairs also serve a fashionable function. In various cultures hairs and hairstyles express the status of human beings. Hair-care products are the most important cosmetic products sold in order to make a person (even) more beautiful and attractive.

Hair serves various functions

It holds in bodyheat in cold weather and it insulates the skull from the heat of the sun.
Eyebrows prevent sweat from dripping into your eyes.
Hairs in your nose and ears filter out dust and small insects.
Eyelashes work with the eyelid to warn us that there is an object near the eye. Eyelashes also protects our eyes from sun and wind.
Hair helps to reduce friction in skin-to-skin contact (under your arms).
However, the most important role of body hair is communication!

The development of the hair begins in the embryo and by the sixth month the fetus is covered by a growth of fine hair (lanugo hairs). Hair follicles are never added during life. Though people have more hair follicles as a chimpanz human hair is very fine and short making us look "hairless."

The hair follicles develop more different hair types during our lifes depending on the stage we are in. At puberty coarse hair develops in the in the armpits and and over the pubic region of both sexes. Male facial hair begins to grow coarse to form the beard.

Hair growth

Men naturally suffer more from hairloss and it can start at a very young age... more

Normal hair fall is approximately 100-125 hairs per day. Fortunately, these hairs are replaced. True hair loss (Effluvium) occurs when lost hairs are not regrown or when the daily hair shed exceeds 125 hairs. In case you should have one or more bald patches on your scalp you will be suffering from Alopecia areata (see photo right). The terms hair loss and hair diseaeses should be used carefully.

Hair growth is fastest from the age of sixteen to the late twenties.

On most people hair is genetically programmed to grow and is hormonally dependant. The hair on the top of your head grows faster than your eyebrows or eyelashes.

Hair on the scalp grows about .3 - .4 mm per day or about 6 inches per year. Men who will never cut their hair will have a length of .40 - .50 cm. Women who will never cut their hair can achieve a length of .70 - .80 cm.

Hair lengths of more than ne meter are rare. Exceptional lengths can be achieved!
<<< more information about hair records - the longest hair in the world >>>

The average number of hairs on the head is 100.000. Blondes have the most hair! It is possible to determine the average amounts of hair per hair colour:

Blondes = 140.000   - Brunettes = 100.000   -  Redheaded = 85.000


Hair growth cycle scalp

Hair grows in three stages, consequently you never have a full head of hair as some hair is in the resting stage of growth. Each hair follicle undergoes a cycle of activity. The hair grows to a maximum length, then hair growth ceases and the hair is shed and replaced. At any one time we only have around 85% of our hair on our head, the rest being in the resting stages. The hair growth cycle has three distinctive phases:

1. Anagen phase: active growth

The epidermal cells surrounding the dermal papilla form the germinal matrix or root of the hair. These cells are constantly dividing, and as new cells are formed they push the older ones upwards where they begin to change shape. By the time the cells are about one-third of the way up the follicle they are dead and fully keratinised.

A scalp hair will grow actively for between one and a half and seven years (three years being an average growth period). The average growth rate is about half an inch per month. On average 85% of follicles are in the anagen stage.

 

2. Catagen phase: the period of transition

This is the end of the active growth period, and is marked by changes occurring in the follicle. The hair stops growing and becomes detached from the base of the follicle forming a club hair. The hair bulb begins to break down, resulting in the follicle becoming shorter. A small section of the outer root sheath remains in contact with the group of cells that formed the papilla.

This period of breakdown or change lasts about three weeks. As the inner root sheath breaks down, the hair remains in the follicle due to its shape. On average, 1% of follicles are in the catagen stage.

3. Telogen phase: the resting phase

The section of remaining root sheath still in contact with the papilla is known as the secondary or root germ. It is from this germ that a new hair can grow. The shortened follicle rests for about three months. The hair may be brushed out at this time or at the onset of anagen. On average 14% of follicles are in the telogen stage.

After the telogen stage the cycle returns to anagen and the root germ begins to grow downwards and forms a new bulb around the dermal papilla. It is the lower end of the germ that forms the new bulb, producing a new hair. The upper part of the germ forms the new cells that lengthen the follicle below the club hair. The new hair may push the old hair out. Sometimes therefore you may see two hairs in the same follicle.

Stages Phases Condition Period Percentage
1st. stage Anagen Active growth 2 - 6 years bis 90%
2nd. stage Katagen Transition 2 weeks bis 3 %
3rd. stage Telogen Resting phase 2 - 4 months bis 18%

 

 

hair types

Lanugo hair

This is the hair that develops on an unborn baby. It begins to grow about three months after the baby's conception. The hairs are fine and soft, and they grow all over the baby's body. They all grow at the same rate, so the hairs are the same length. Some prematurely born babies are still covered with these downy hairs. Normally they are shed about four weeks before the baby is due to be born.

Vellus hairs

Soft, short, fine and unpigmented hair and is to be find all over the body. Vellus hairs are soft, short and fine hairs, only a centimetre or two long, and contain little or no pigment.

Terminal hairs

Terminal hairs are the long hairs that grow on the head and in many people on the body, arms and legs too. They are produced by follicles with sebaceous glands. In people who have inherited a tendency to baldness the hairs in these follicles gradually become thinner and shorter until they look like vellus hairs.

Intermediate

Known as hair that lies midway (between the extremes of vellus and terminal hair).

 

Hair colour  &  glossy - sleek hair


Our genes determine our hair colour. Which colour, whether they are curly or sleek, thick or tin or when the first grey hairs appear, everything is genetically determined. The melanocyte cells, which are found in the basal layer of the epidermis, manufacture a special pigment called melanin, which helps to determine the hair and skin pigmentation.

Two different forms of the pigment melanin:
1. Eumelanin: produces the black and brown skin & hair pigmentation.
2. Phaeomelanin:produces the red and blond skin & hair pigmentation.

Those two forms of melanin are often both present together and occur in varying proportions:

• Blond hair contains little eumelanin and lots of phaeomelanin.
• Dark hair contains lots of eumelanin and little phaeomelanin.
• Red hair has also little eumelanin and lots of phaeomelanin.

"Hairy"  visitors


Everybody has million of hair mites living in their hair or on their skin. They live in the hair follicles of 98% of all people and feed on oils, hormones and fluids around the follicle. They are transferred from host to host through hair, eyebrows and on the nose.

Also head louse/ head lice (see photo right) feel at home in our hair. They are usually find on our scalp and live on blood from the host which they get by biting through the scalp. Treatments like... more

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