www.4haircare.com.au Each hair on your body grows from a hair follicle, a tiny, saclike hole in your skin. At the bottom of each follicle is a cluster of special cells that reproduce to make new hair cells. The new cells that are produced are added on at the root of the hair, causing the hair to grow longer.
|A micrograph of a hair shaft. Note the layered cuticle on the shaft and the bulb at the bottom.
–Micrograph courtesy of Paula Sicurello/U.C. Berkeley Electron Microscope Laboratory.
The living tissue that makes your hair grow is hidden inside the hair follicle. The shaft, the part of a hair that you see, is made of cells that aren’t living anymore. That’s important to know when you are messing with coloring or perming or straightening your hair. If you cut yourself, your skin can heal, since it’s living tissue. If you damage your hair, it can’t heal. You just have to do what little you can to repair the damage or cut the damaged hair off and wait for more hair to grow back.
Each hair shaft is made up of two or three layers: the cuticle, the cortex, and sometimes the medulla. The cuticle is the outermost layer. Made of flattened cells that overlap like the tiles on a terra-cotta roof, the cuticle protects the inside of the hair shaft from damage.
The hair cuticle is the first line of defense against all forms of damage; it acts as a protective barrier for the softer inner structure including the medulla and cortex. The cuticle is responsible for much of the mechanical strength of the hair fiber. A healthy cuticle is more than just a protective layer, as the cuticle also represents the structure that controls the water content of the fiber. Much of the shine that makes healthy hair so attractive is due to the cuticle.The hair cuticle is also said to be water resistant.
Cuticles are often damaged by excessive mechanical manipulation such as brushing, using heat (like using curling irons) or chemical processing (like perms or texturizers). Everyday elements, such as the sun or wind can also cause wear and tear on your hair and damage the hair cuticles as well.
Although the cuticle is the outermost layer of the hair, it does not give the hair its color because it has no melanin, which is the pigment responsible; the color of a person’s hair depends on what type of melanin they have, which is found in the cortex.
To feel the cuticle, just pinch a single long hair between your fingers starting up near the root. Pull the hair between your fingers and feel how slick and smooth it is. As you move from root to tip, you’re running your fingers in the same direction as the cuticle layers. Now start at the tip of the hair. In this direction, the hair may feel rougher; it may squeak as it passes between your fingers. You’re running your fingers against the grain, and you’re bumping into the edges of all those flattened cuticle cells.
It’s handy to know how different conditions affect this protective layer on the outside of each hair. Chemists talk about solutions that are acidic (like vinegar or lemon juice) and ones that are alkaline (like a mixture of water and baking soda). In an acid solution, the cuticle cells shrink and harden. In an alkaline solution, the cuticle cells swell up and soften.
Just to confirm the response of the cuticle to acidic and alkaline solutions, I tried soaking one strand of hair in water and lemon juice and another in water and baking soda. I rinsed both strands carefully. When they dried, the hair from the lemon juice bath felt smoother and looked shinier.
Underneath the cuticle is the cortex, which is made up of long proteins that twist like the curly cord on a telephone. Try stretching a hair and you’ll find that it’s elastic—it stretches before it breaks. When you stretch a hair, you are straightening the coiled proteins in the cortex. When you release the hair, the proteins coil up again. The pigments that give your hair its natural color are tucked among these protein strands and protected from the elements by the translucent layer of cuticle cells.
When you get split ends, you’re seeing the cortex at its worst. You’ve worn away the protective cuticle on the tips of your hairs with harsh treatment like hard brushing or too much sun and water. Without the cuticle, the fibers of the cortex fray like the strands of a rope. Since the cortex can’t heal itself, the only way to get rid of split ends is to cut them off.
In the center of some hairs is the medulla, a soft, spongy mass of tissue. Coarse hair generally has this layer, while fine hair usually doesn’t. The presence or absence of a medulla doesn’t have much to do with how your hair behaves when you wash or color or curl it, however, so you don’t have to worry about it.
To fill the gaps between the protective cuticle cells and to keep your hair shiny and flexible, glands adjacent to the hair follicle produce a kind of natural hair conditioner called sebum. Unfortunately, that sebum, which is an oil, also makes dirt stick to your hair. When you shampoo your hair, you wash away this protective oil and the dirt that clings to it.
Hair is made up of 88% protein known as keratin. This is why protein treatments can help preserve the length if you aren’t protein sensitive. Within the keratin our hair contains 4 different bonds including the Hydrogen Bond, Salt Bond, Cystine Bond, and Sugar bond. Each bond is important in understand your hair’s growth, health, and how to maintain healthy hair.
Hydrogen Bond – This is what makes the hair elastic and allows you to temporarily change the shape of your hair with the aid of water (i.e. wet sets, twist outs on wet hair, etc.). These bonds are responsible for 35% of the hairs elasticity and 50% of it’s strength. During a chemical process such as a relaxer the hydrogen bond is broken down and reformed making the hair more prone to breakage.
Salt Bond – To sum this bond up in lamen terms, this bond is also responsible for 35% of the hair’s elasticity and 50% of it’s strength.
Cystine Bond – Also known as the sulfur or disulfide bond of the hair. This bond is responsible for holding the actual hair fibers in place and the hair’s toughness.
Sugar Bond – This bond gives the hair some toughness and strength (about 5%) and even provides some moisture.