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.
The cortex makes up the majority of the hair shaft. The cuticle is a tightly formed structure made of shingle-like overlapping scales. It is both the cortex and the medulla that holds the hair's pigment, giving it its color. Hair Growth Cycle. Hair on the scalp grows about .3 to .4 mm/day or about 6 inches per year.