The Functions of the Hair

A breif slideshow on three functions of the hair.

1. The Functions of the Hair This slideshow is to tell you about three functions of the hair: How our hair keeps us warm How our hair protects us Racial characteristics of hair structure and colour

2. How Our Hair Keeps Us Warm The main function of the hair is the either warm us up or cool us down. When we are hot, the hair lies flatter against the skin and therefore allowing less heat to break through. When we are cold, the hair stands on end to trap more heat and warm up the body. The way the hair moves is through the arrector pili muscle located in the dermis layer of the skin. This tiny muscle controls how the hair lays on the skin. When warm, the hair lies flat. When cold, the hair stands up and the skin breaks into goose bumps, which is the skin raising up to collect more warmth.

3. How our hair protects us Hair grows all over our bodies – the only places it doesn’t grow are on our lips, the soles of our feet, our palms and our eye lids. Hair grows faster during the Summer and slower at night than during the day. The ways in which our skin protects us are Regulating our body temperature Controlling the loss of life sustaining fluids such as blood and water Protects us from the sun’s damaging ultra-violet rays

4. Racial characteristics of hair structure and colour Genetically, Africans have more variety than other races.  Every time a group advanced out of Africa, or from one isolated area to another even more isolated, another batch of genetic variations was left behind.  But on the surface, it's Caucasians that have the most variety, for the simple reason that they have a lot less melanin, which takes the darkness out of their skin, hair, and eyes to reveal other possibilities. Hair colour is determined by 4 to 6 genes, each with several alleles, some with incomplete dominance (i.e. not a matter of one thing or the other, but perhaps a mix of both - like pink carnations).  The basic genes involved are for black hair (with a recessive allele for not-black), one for brown hair (with a recessive for blond), and one for red hair (with a dominant allele for not-red).  Some of these genes are close to eye colour genes on chromosomes 15 and 19, and tend to go along with those genes, which is why we tend to see certain combinations of hair and eye colour more frequently than others .

5. Racial characteristics of hair structure and colour (cont.) Black is the most common hair colour in the world, and is due to a large amount of eumelanin .  Brown is also common, and is due to eumelanin mixed with a bit of pheomelanin .  Blond is only found in about 2% of the world's population.  It is due to very small amounts of melanin.  Slight amounts of black, brown, and red make for all the variations we see in blonds - such as ash, flaxen, and strawberry blond.  And red hair is the rarest of all, about 1% of the world.  It is due to high levels of pheomelanin plus low levels of eumelanin . If you are curious, grey hair is due to nothing but a little black melanin, and white hair is a matter of no melanin at all . Light coloured hair is found primarily in Scandinavia and the Baltic sea area.  Blond and red hair was probably more common in Europe centuries ago (as witnessed by Greek and Roman accounts), but being recessive, it has slowly receded northward.  But you can still find blonds and redheads in places like Afghanistan and northern Pakistan, where the descendants of Indo-European invaders live.