The human body contains roughly 5,000,000 hair follicles. The function of each hair follicle is to produce a hair shaft. The function of human hair depends on the part of the body from which it grows. Human hair performs several functions. It protects the skin from environmental influences. It responds to external input and translates this information into neurological impulses that are interpreted as sensory stimuli by the brain. Scalp hair is also the only part of the human body that can be readily and consciously modified to change an individual's external appearance. So it also serves as an important means of allowing individuals' to socially communicate.