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The Human Body: Hair

By Edited Oct 27, 2015 0 0

Hair, at its basic function, helps to regulate our body temperature and keep ourselves warm. But the hair on our head can be our obvious defining feature, which can be stylized, cut or coloured to suit our personality of mood. We have about five million hair follicles all over our bodies, covering everything except our lips, the palms of our hands and the soles of our feet.

Why do we Have Hair?

There are different theories as to why we have body hair, but the general consensus amongst scientist is that it is remnant from our primitive days when we didn’t have clothing and therefore relied on our thicker body hair to keep us warm.  Some hair functions are clear. Our eyebrows are shaped like an arch to channel water such as sweat or rain to the side of our face and away from our eyes. Our eyelashes protect our eyes from dust and sand. Our nose hairs are responsible for filtering out any dust particles in the air to stop them going down into our lungs as we breathe in. 

How Does Hair Grow?

Hair follicles are little pits in the skin. At the bottom of each hair follicle there is a hair bulb, which contains cells that divide, forming the hair and pushing it upwards out of the skin. These cells are loaded with keratin, a tough protein that also makes up our finger and toenails. When the cells are pushed upwards, they die, leaving behind the layers of keratin which make our hair. Glands in the base of the hair follicle below the skin’s surface produce oil that keeps the keratin hair shaft flexible and moist. Because there aren’t any nerves in your hair, it doesn’t hurt when you cut it or heat it up to straighten or curl it. But we do have nerve in the skin surrounding each individual hair follicle, so if someone yanks on our hair, messages from these nerves are sent to the brain, telling us that it is painful.

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Hair Colour and Shape

Light or Dark? Curly or Straight? Why does our hair change colour?

Hair follicles are coloured by pigments called melanin. Eumelaniin in a follicle makes a hair brown or black, while red or blond hair is produced when the pigment phaeamelanin is present. Grey hair is a result from when follicles are unable to produce any pigment anymore. These follicles are actually white, but next to the darker strands of hair, appear grey.  Asian people have the thickest hair strands and among Caucasian people, red hair stands are considered the thickest and blond the finest.

Furthermore, the straightness or curliness of a person’s hair is determined by the shape of the strand. Straight strands of hair are round, in curly hair they’re oval, and in wavy hair they are elliptical. Curly, wavy or straight hair is also hereditary, as it comes from the genetic make-up of your parents. 

Well That Was a Hair-Raising Experience!

Ever had the feeling of your hair standing on end? Ever had a hair-raising experience? This feeling is usually associated with when we have an encounter that either excites or frightens us. However it is actually related to our physiological state of mind. When we are scared or angry, or feel like we are in danger, little muscles called the arrector pili, which are attached to each hair follicle, automatically tighten. This has the effect of making our hair stand straight up, particularly noticeable on the short hairs on our arms. The same phenomenon is also present when we are cold. When our body temperature drops, the muscles around our hair follicles form small bumps, also known as good pimples or goose bumps. This helps to trap warmth in our body instead of allowing it to escape.

Losing Our Hair

Because our hair growth patterns continuously change throughout our lifetime, we all will lose hair. When we are born, every square centimetre of our scalp has roughly 1000 hair follicles. As we grow, this scalp skin containing theese follicles stretches over our growing skull, which drops our hair count down to around 200 follicles per square centimetre. One average, 2000 scalp follicles stop working every 10 years, although the rate can vary person to person. It is more obvious in men, who are more likely than women to go bald or partially bald. Baldness is an inherited trait, but can skip several generations and can be inherited from either side of the family. Male baldness usually begins between the ages of 18 and 30. The hormones that make follicles from which hair grows begin to shrink. Eventually, they become so small they cannot replace lost hairs. The follicles are still alive but are no longer able to perform their tasks properly, so hair that falls out cannot be regrown, which in turn leads to balding.

Hair Facts

  • Strands of hair grow an average of 12 centimetres per year.
  • In the 1600s in England it was considered lucky to have a haircut on Monday, and unlucky on a Friday or Saturday.
  • A single strand of hair can support up to 100 grams in weight.
  • In 1997 Hoo Sateow’s hair was officially measure at 5.15 metres and is considered the longest in the world. In 1929 at the age of eighteen, Sateow became sick and was forced to cut his hair. After he recovered from his illness, he vowed never to have it cut again.
  • The first liquid shampoo available was called Dop, which first came out in 1952.
  • Every day we lose between 30 and 100 hairs from our scalp, each of which usually started growing several years earlier.
  • Having an iron deficiency can cause hair loss.
  • Hair is the fastest growing tissue in the body, second only to bone marrow.
  • An adult will grow 35 metres of hair fibre every day.

If you are interested in finding out more interesting facts about the human body, you can continue learning about muscles or eyes.

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