Good Hair. Libby Peacock

products, with a section dedicated to the latest scientific breakthroughs and surgical solutions.

       8. A male perspective

       A focus on choosing the right style, making the most of greying or thinning hair and the latest hair-loss solutions.

       Glossary

       Useful addresses

       References

       Photographic credits

       Index

      Hair as we know it

      The English language is rich in hair-related expressions, for good reason: our hair is not only useful, it also reflects who we are. So, when we nitpick about small things, we split hairs; when we have a narrow escape, we escape by a hair’s breadth; and when we have a good time, we let our hair down.

      Hair gives away clues about our personalities and carries cultural connotations. Pious Christian nuns cover their hair. Muslim women wear headscarves to hide theirs from the eyes of all men but their husbands and immediate family. In India, hair is regarded as one of the most important aspects of feminine beauty. In some faiths, hair is cut during mourning. Several ancestral cultures still believe hair has magical powers; even in modern European countries some parents keep locks of their babies’ hair.

      Legends abound about hair: when Biblical hero Samson’s long hair was cut, he lost his power; and, while blondes have more fun, redheads are believed to have a fiery temperament. Thankfully, many of these perceptions are not scientifically supported!

       Assuming about 80 per cent of scalp hairs are in the active growth phase at any given time, a human produces about 9km (5.6miles) of hair every year.

      Your hair’s structure

      Given that healthy hair is a reflection of one’s general health, it is ironic that the visible part of a hair – the hair shaft – is physiologically speaking, dead, with only the tiny part underneath the scalp (the root or dermal papilla) consisting of living hair-forming cells known as trichocytes and keratinocytes. The dermal pa-pilla, nourished by a network of blood vessels and nerves, is nestled in a tubelike hair follicle and surrounded by what is known as the bulb. The bulb is embedded about 4mm (0.2in) in the subcutaneous fat of the scalp. The outer layers of the hair bulb are known as the outer and inner root sheaths. It is in the dermal papilla that most hair growth takes place. In order for hair to grow, cells have to reproduce. This takes place around the dermal papilla in what scientists call the zone of proliferation.

      Each hair has a protective outer cuticle, made up of tiny overlapping scales, often compared to miniature roof tiles, and a thick cortex that lies under the cuticle and consists of the protein keratin. Keratin is also found in human skin and nails, as well as in the feathers, claws, hooves and wool of birds and animals.

      Hair also contains the elements carbon, oxygen, nitrogen and sulphur and a tiny percentage of the trace elements zinc, iron, copper and iodine. Other components include fats, and water, which makes up about 12 per cent of a hair’s weight.

      Some types of hair – particularly thick, dark hair – also have a central medulla, which when inspected under an optical microscope, looks a little like a central canal. Some scientists believe it enhances the thermal-insulation properties of hair. Others speculate that the medulla carries nutrients to the cuticle and cortex, while yet another theory is that it contributes to the shine of hair.

       The anagen phase: Active growth takes place in the hair bulb. This phase can last for years, often between three and seven years.

       The catagen phase: This is a relatively short phase, during which the follicle stops producing hair and the hair bulb starts to break down.

       The telogen phase: A resting phase during which there is no growth and the hair is ready to be shed.

       A new anagen phase: The old ‘club hair’ is ready to fall or be pushed out.

      THE GROWTH CYCLE OF HAIR

      Hair passes through a growth cycle broken up into three main phases: an active growth phase known as the anagen phase; a short, transitional catagen phase during which the hair stops growing and the hair bulb begins to break down (but there is still cellular activity in the papilla); and a resting telogen phase when no growth takes place and the hair is ready to be shed. The duration of the different phases varies from person to person, but the anagen phase can last anything from three to seven years, and in some cases even up to nine years. The catagen phase lasts roughly two to four weeks, while the telogen phase is estimated to last three to four months.

       Function of the cortex and cuticle

      The cortex cells give hair its strength and elasticity, while the cuticle reflects its condition.

      If the protective scales of the cuticle are undamaged and lie flat, hair appears shiny and healthy, and is soft and manageable, but if they have been broken or damaged through straightening or colouring, hair looks dull and unhealthy. Environmental factors, including sunlight, air pollution and wind, can also damage the cuticle. The more damaged it is, the more tangled hair becomes and the more difficult it is to brush. Hair with smooth cuticle surfaces, on the other hand, reflects more light than hair with rough cuticle surfaces, which is why straight hair appears glossier than curly hair.

       Different types of human hair

      ■ Lanugo hair is the first hair to be produced by the hair follicles of a developing foetus. It normally covers the foetus until the seventh or eighth month of gestation, is fine and soft and contains no medulla and no pigment. After it has been shed, it is replaced by vellus hair and terminal hair.

      ■ Newborn babies’ bodies are covered with vellus hair, although they have terminal hair on their heads and eyebrows. The fine hair on parts of some adults’ bodies is also vellus hair. These hairs are short, just a centimetre or two long, and they are soft, with no medulla. Occasionally, they contain pigment.

      ■ Terminal hair, which grows on the head and also makes up beards, eyelashes and armpit hair, replaces vellus hair. These hairs are longer and coarser than vellus hair, often have a medulla and are usually pigmented.

       A touch of colour

      Melanin,