How does hair grow and other hairy facts!

Hair Biology - Hair fibre

The fibre of our hair

Keratin, a protein, makes up your hair. It's the same protein that nails, claws, beaks, quills, and hooves are made of. One strand of hair is composed of many unimaginably thin coils of protein twisted together to form bundles. The bundles are grouped together into more bundles to form one rope of keratin - which is what one strand of your hair is.

The units that make up your hair's protein are little groups of atoms known as amino acids. Every hair is built amino acid by amino acid, looking like beads on a string. Each amino acid is like a different type of bead placed in a specific sequence on the string, and it reacts to its neighbors a bit differently. One amino acid might be irresistibly attracted to a particular neighbor down the string from it. When attracted, the two amino acids cling to each other. When one amino clings tightly to the amino down the way, it changes the shape of the string when they get together.

Amino acids feel this attraction at regular intervals up and down the strand. When they're all bonded to one another, the pattern they create causes the strand to take the shape of a coil. This coil is an alpha helix, the same shape our DNA takes. Four of these alpha helices are twisted together into a structure called a protofibril. Eleven protofibrils are twisted together to make up one microfibril. Hundreds of microfibrils are bundled together and embedded in a protein-cement matrix to form one macrofibril. Bundles of macrofibrils make up the cortex, the main core of the hair. One strand of hair is about ten macrofibrils across.

What this means is that one single strand of your hair is composed of hundreds of thousands of surpassingly thin strands of fiber, twisted and bonded together. Every strand of hair you produce is an intricate marvel of construction. A string of amino acids builds each hair into the twists of an alpha helix. The alpha helix is the building unit of every strand of hair. Because of its coiled nature, when you stretch a strand of hair, the helices unwind to accommodate the stretching without breaking. The strand can unwind to about 30 percent of its length and still return to its previously coiled shape without damage. When stretched, the twisted shape of the helix changes from coils to pleated sheets, like an accordion fold. When released, they spiral back up again.

When your hair is stretched beyond this amount, the helices are stretched too far and break. Knowing this is crucial when you're combing or brushing your hair. When you pull a comb or brush through your hair, your hair is stretched. If you do it gently, it springs right back. If you use lots of force to get a brush or a comb through your hair, such as when your hair isn't slippery enough, the comb's teeth are too close together, or heavy force is exerted to get the comb or the brush through your hair in a hurry, your hair is stretched and damaged. If you use a brush such as a Denman, which has some give to it because of its flexible rubber base, the give comes from the brush instead of your hair. If you use, or someone uses on you, a hard plastic comb or moves through your hair with force, this means all the give must come from your hair alone. This will damage your hair. Keeping this in mind is a vital way to prevent needless damage getting inflicted on your hair.

The bonds

Not only do the bonds of each strand of your hair hold it together, but the way these bonds are composed also explains why your hair behaves as it does. The bonds determine how much your hair curls, why it frizzes in humidity, and why a set holds better when it's done with wet hair. There are three main bonds within and between all of those alpha helices that determine the structure and behavior of your hair: hydrogen bonds, salt bonds, and disulfide bonds. The coils are shaped by the interactions between the bonds, both within their structures and with neighboring coils. These bonds repeat down their entire lengths. Because of their massive numbers, they are powerful.

Hair Biology - How much of hair is growing at one time

Hair is dynamic. All of the hair on your head is at one of three stages: growing, resting, or packing up and leaving. At any given time, as long as you're in good health, most of your hair is growing. Each hair grows for about two to seven years, and nearly 90 percent of your hair will be in this growth stage.

Your health and your genes determine how much time your hair spends growing. The more time each hair has to grow, the longer your hair will be. Most people have hair that can grow long enough to reach down to the middle of their backs. They just don't realize it. Hair often doesn't seem to grow when it's being damaged and breaking off at the same rate it grows.

While a few people can grow hair long enough to step on, there are others who have hair that's genetically programmed to reach only a little past their shoulders before each hair's life span ends.

During the resting stage, your hair prepares for the end of its time on your scalp. Only about 12 percent of your hair is in this holding pattern at a time. After three to eight weeks of resting, your hair has said its goodbyes and is now ready to go. After a hair falls out, the follicle rests for about twelve to sixteen weeks before building another hair and starting the process all over again.

Each follicle is capable of about twenty of these cycles before it runs out of steam and stops producing. We shed about 100 to 150 hairs a day. Provided that you're in good health, this equals about 700 to nearly 1,050 hairs lost a week. This means that if you comb your hair once a week, there will be a mat the size of a tiny animal left in your comb. This is totally normal.

It's important to know the average life span of a hair, because you need a marker to determine when your hair is healthy enough to have most likely reached its maximum length. This means it's grown its entire life with so little damage that it didn't break off before it could grow as long as it was genetically programmed to.

Hair that has grown to an average maximum length lives about six years. This is about thirtysix inches, or lower-back length, depending on how fast it grows. If you can't get your hair to grow to its maximum length, it means that in some way your hair is still being damaged.