Hair Structure And Growth

Hair Structure

Each hair is a complex cellular structure and varies from one person to another. The structural form is basically the same: each strand, no matter how fine it may look, consists of three layers.

The outer layer, or cuticle, is made up of overlapping scales which protect the inner layers.

The next layer, or cortex, is made up of long thin cells, and is the most important because it gives the hair its elastic resilience, and contains the pigment which provides the coloring.

The innermost layer, or medulla, is spongy tissue and the cells sometimes contain granules of color pigment.

The part of the hair which is visible above the skin is the shaft, and the part that lies beneath the scalp is the root. The root is not a single unit; it is enclosed in a sac called the hair follicle, and at the base of this is a tiny nodule called the papilla. The papilla is the store house for nourishment of the hair strand. If you pull a hair out by the root, although there is a tiny globule of white at the end of it, you leave behind the papilla which will eventually manufacture and nurture a new hair.

This is the reason why plucking is never a permanent way to get rid of unwanted hair, and also why hair loss through abuse and breakage will eventually be replaced.

Interlocked to the follicles are sacs called sebaceous glands which contain sebum, sebum lubricates the hair and gives it it's gloss and suppleness. An under active or blocked sebaceous gland means dry hair, an over active one means oily hair.

Cuticle or Outer layer of hair showing layers of overlapping scales. By Jan Homann (eignes Bild) [Public domain], via Wikimedia Commons

Cross-Section of the hair shaft

Diagram showing hair structure of the follicle below the epidermis.

Hair Growth

Each strand of hair grows out straight or curly depending on the inner structure of the root. If the root is smooth, the hair comes out as a perfect cylinder and is straight. If the root is distorted, the hair shaft is more oval, at times quite flat, and emerges as waves and curls.

Whatever the texture, you usually have between 90,000 and 140,000 individual hairs on your head. Blondes, because their hair is finer, have the most; then dark-haired people, whilst redheads have the least although their hair is the thickest and therefore will appear the most abundant.

The life-span of a single hair can vary from a few months to several years. Each strand has its own cycle of growth, then a period of rest which ends in its falling out and being replaced by a new hair. This process is evenly distributed at different stages throughout the head and it is perfectly normal to lose a certain number of hairs every day.

On average, hair grows at the rate of half an inch (13mm) a month, though this slows down as we get older. It grows faster during warm weather, and faster at night.

The reason why some women can grow hair to their waists is because they have the combination of a quick growth rate and a relatively long life-span for each hair. It usually happens when you are young and in good health.

Nothing can make hair grow faster and most hair, after reaching a length of ten inches (255 mm), slows down to half the normal rate of growth.

It is untrue that cutting will encourage the hair to grow. It may seem this is so simply because, having got rid of the split and damaged ends, the hair appears thicker and healthier.

Hair Color

Hair color is determined by three pigments – black, red, yellow. Black and dark brown hair are concentrations of black; red begins to show up in brown hair; light hair contains traces of yellow; red hair is mostly red pigment with black or yellow shadings; blonde hair is yellow with traces of red.

Hair doesn’t really turn grey, but loses its color. The middle section of the hair shaft stops producing pigment and fills up with colorless air bubbles, but because the white hairs are inter-mixed with the colored ones, the general effect is grey. The age at which hair turns grey is usually hereditary. It cannot turn grey overnight but it can lose its color quickly due to illness or emotional shock.

Healthy Hair

We are inclined to forget that healthy hair is part of a healthy body, and directly affected by physical metabolism and emotional balance. Its texture may be determined by genes but its strength and condition are determined by what you eat. A high protein diet with lots of fresh fruit and vegetables is good for hair. Foods containing vitamins of the B complex are essential. Important too are vitamins A and C.

Of the minerals, iron, iodine and copper are the most beneficial, and the lack of iodine can be most harmful. A supplement of brewers’ yeast tablets is recommended for anyone with a hair problem. In some cases, if premature greyness has been caused by nutritional deficiency, it can be helped by large doses of vitamin B.

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