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Hair: The Basics

Sources: Sandeman, Goldman, Better Hair Through Chemistry, Tips of all sorts, 


    "On your head, you have over 100,000 hairs" (Sandeman).Every hair grows from a hair follicle. A hair follicle is a small hole in your skin.The part of hair that grows above the hair follicle is called the hair shaft. It is made of cells that are no longer living. The hair roots are anchored into the skin. A root of an individual hair forms a tiny long tunnel, which reaches down to the lower layers of skin. At the end of the root, there is a papilla. The papilla is the center of growth for hair, made up of a cluster of special cells. New hair is produced when these cells reproduce. This is also the site where hair takes up all the nutrients from the blood.
    The type of hair you have is determined by your hair follicle's size and shape. Large follicles create thick and heavy hair, while narrow follicles produce fine and thin hair. The shape of the follicle decides how straight or curly hair is. Straight hair is grown from round follicles, oval follicles force hair to be and become wavy and flat folicles coil hair into tight curls. 
    Each hair on your head has two or three layers. They are the cuticle, the cortex and sometimes the medulla. The outermost layer is the cuticle. It is flattened cells that overlap like shingles on a roof. The function of the cuticle is to protect the inside of the hair shaft from damage. The cortex rests underneat the cuticle. It is made of long proteins that are curled up. The cortex is what causes a hair to stretch before it breaks. When it is stretched, the coiled proteins are being straightened. If you let go of it after it is stretched, the proteins will coil up again. The pigments which give your hair its color are tucked into the protein coils, and protected by the cuticle. Some hairs contain a medulla, a soft, spongy mass of tissue. Usually it is coarse hair that has this layer, while fine hair usually doesn't. However, the presence or absence of medulla has no effect on how hair behaves.
    To keep hair shiny and flexible, glands near then hair follicle produce sebum, a form of natural conditioner. Sebum is an oil, and it makes dirt stick to your hair. Shampooing washes away this protective oil and any dirt that may cling to it.
    Hair growth has three phases: anagen(growing), telogen(resting) and catogen(falling out). The anagen phase lasts the longest, normally lasting 3-5 years. After the growth phase, a resting period of 1-2 weeks follows and then turns into the catogen phase. The catogen phase lasts 2-3 months. Once the whole cycle is completed, the old hair falls out and a new one replaces it from the same follicle. On average, hair grows 0.25 to 0.40 millimeters a day. Therefore, hair normally grows 2.1 mm a week, 1 cm a month, and 12 cm a year.
    Split ends occur in the cortex. The protective layer of the cuticle has been worn away. Without the protection of the cuticle, the proteins of the cortex fray like a rope strand that's been undone. The only way to get rid of split ends is to cut them off.
    Hair needs many nutrients to be healthy. A few of the major ones are listed below.  
    Vitamin A- promotes healthy scalp
    Food Sources: dark green, orange and yellow fruits and veggies
    Vitamin B complex- regulates the secretion of oil, keeps hair healthy and moisturized
    Food Sources: cereals, tomatoes, lean meat, liver, kidney, Brewer's yeast, eggs and green veggies
    Minerals like zinc, iron and copper- promote healthy hair
    Food Sources: Zinc-lean red meat, chicken, pumpkin seeds and green veggies; Iron- beef, dried apricotes, lean red meat, parsely, eggs, wheatgerm, and sunflower seeds; Copper- seafood, egg yolk and whole grains
    Protein- since hair is made up of 97% protein, eating enough of it gives hair a natural shine
    Food Sources: lean meat, grains and soy.