Hair root is the part of hair under scalp, which is called the soft keratinose, and the hair shaft is the part of hair above scalp, which is called hard keratinose, and 97% of hair is keratinose and 3% of it is carbohydrate.
Hair grow our of the hair follicles, which has complex structure and many epithelial cell in the hypoderma. The cells of hair papilla in the front of the hair follicles can continually divide to create new cells to make the soft keratinose.
When the soft keratinose keeps growing, dehydrating, keratinizing and stretching out of the scalp, it will be farther and farther away from the nutrition source, and the hair will get easily injured if suffered from the damage of outside, so hair can be healthy only by taking good care of hair shaft.
Furthermore the live part of the hair is only the hair papilla, which is on the top of the hair follicle and has 600 capillary vessels and nerves, that’s why haircut does not hurt but pulling out hair hurts. There are 18 kinds of amino acid can be decomposed from the keratinose of hair, so we can say the group of amino acid is the material of hair.