Hair exists both above the surface of the skin and below it. Hair can be categories by its detailed structure and by two key divisions or groups. Hair can be classified as that part that resides about the skin and that part that resides below the skin.
The part of hair that sticks out from the skin is called the Hair Shaft.
The part of hair that resides below the surface of the skin is call the hair root.
The hair follicle is a tiny opening in the skin that looks like a small tube. The follicle surround the hair root. No many how many hairs a human has, their hair has its own follicle.
At the base of the follicle is what is defined as the papilla which is embedded deep in the dermal layer of the skin. The papilla is deep in the dermal layer of the skin and is feed by blood vessels and a network of nerves.
The hair bulb is positioned right above the papilla and and fits over the papilla as tightly as a glove. While the hair bulb is wide at the base it taper gradually narrowing as it approaches the actual surface of the skin.
The papilla which is nourished by the blood vessels in turn nourishes the hair bulb.
The average growth rate of hair follicles on the scalp is .04 cm per day