Fast Evolution Affects Everyone, Everywhere. 1  Dec. 6, 2016 â Rapid evolution of other species happens all around us all the time -- and many of the most extreme examples are associated with human ...
Hair is simple in structure, but has important functions in social functioning. Hair is made of a tough protein called keratin. A hair follicle anchors each hair into the skin. The hair bulb forms the base of the hair follicle. In the hair bulb, living cells divide and grow to build the hair shaft.
1 Hair is composed of the following structures: 2  The hair shaft is the portion of the hair that is visible on the surface of the skin. 3  The hair root is the portion of the hair that penetrates the skin (epidermis and dermis).  The hair follicle is the sheath that surrounds the hair in the skin.