Answer:
Hair grows by forming new cells at the base of the root. These cells multiply to form a rod of tissue in the skin. The rods of cells move upward through the skin as new cells form beneath them. As they move up, they're cut off from their supply of nourishment and start to form a hard protein called keratin.
Step-by-step explanation:
Blood from the blood vessels in your scalp feeds the root, which creates more cells and makes the hair grow. The hair gets pushed up through the skin as it grows, passing an oil gland along the way.
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