STRUCTURE OF THE HAIR
Hair is made up of dead cells.
On our heads, we have hundreds of thousands of follicles, pore-like structures within the scalp that produce hair. Each follicle produces many hairs throughout our lifetime.
Live hair cells are generated inside the follicle by the papilla. As the new cells grow, the older cells die and are forced along the follicle towards the scalp. The dead cells are compressed to form a protein called keratin. The hair shaft that we see is the keratin emerging from the scalp. Finger-nails are made of keratin, too.Each hair consists of keratin, small amounts of water and a binding agent, which holds the keratin and water together.
The Structure of Hair
Hair is made up of several layers:
The outer, protective coating of the hair is formed from overlapping scales and can be several layers thick. These scales are what makes the hair flexible. The outer coating is translucent, which allows the colour of the hair (from the ...view middle of the document...
The cortex determines the colour of the hair. There are two pigments:
melanin, which gives us brown and black
pheomelanin, which gives us yellow and red
Medulla-This is the centre of the hair shaft. It does not play a part in hairdressing.
There are three types of human hair:
is very fine. It helps us regulate the temperature of our bodies by aiding the evaporation of perspiration. It grows everywhere on our bodies except for our lips, the palms of our hands, soles of our feet and our eyelids.
Primary hair has a number of special features:
it has no medulla;
there is often no pigment, which is why primary hair can be hard to see;
it is rarely more than half an inch long; and
it has no arector pili muscle to hold it up.
Secondary hair is short, bristly and coarse. Our eyelashes and eyebrows are secondary hair and it appears in the opening spaces of our ears and noses. It is senstive to touch - think about how your eyelids blink to protect your eyes if you touch your eyelids. Our eyebrows also protect our eyes by preventing sweat, water and oil from running down the scalp.
You can identify secondary hair by a number of special features:
it grows straight out from the skin;
it has no arector pili muscle;
it has a large medulla;
it is often curved, such as eyelashes;
it is usually between half an inch and an inch in length; and
it usually increases in density as we get older.
This is the longer hair that grows on our scalps. In adults it appears under the arms and in the groin area and, in men, on the beard and moustache.
Historically, tertiary hair was probably there to keep us warm and protect us from the sun. It has no particular function any more.
Each tertiary hair has its own sebaceous gland to produce oil and an arector pili muscle to lift it up from the scalp.
Tertiary hair grows from the follicle at an angle - this is what we see as the direction of growth. It varies across the head and can change direction creating natural partings or features like a double crown.
it contains pigment - this gives hair its own distinct colour; and
it can be straight, curly or wavy.