This is a small but strong core of cells that can run from the hair bulb to the tip of the shaft. Sometimes the medulla is present only in part of the hair that is below the skin. Also, called the marrow canal, the Medulla is composed of two rows of cells placed side by side lengthwise of the shaft. The Medulla is not hollow. The medulla has little bearing on what we do to the hair shaft.
Hair is composed mainly of a hard chemical substance called keratin.
Keratin, which is a protein, is also present in our nails and in the claws, feathers, hooves, and wool of animals. Hair contains varying amounts of carbon, hydrogen, oxygen, nitrogen and sulfur, whereas dark hair has more carbon and hydrogen, light hair has more oxygen and sulfur. At its free end, the hair tapers to a fine needle point. At the bottom of the follicle or hair sheath in the scalp, the hair swells into a bulb or bowl which fits over the Papilla - a bump or protection in one of the layers of the skin. This bulb is often erroneously called the root of the hair.