Editing Hair (section)

===Warmth===
[[File:Ursus maritimus Steve Amstrup.jpg|thumb|left|Polar bears use their fur for warmth and while their skin is black, their transparent fur appears white and provides camouflage while hunting and serves as protection by hiding cubs in the snow.]]

While humans have developed clothing and other means of keeping warm, the hair found on the head serves primarily as a source of heat [[Thermal insulation|insulation]] and cooling (when sweat evaporates from soaked hair) as well as protection from ultra-violet radiation exposure. The function of hair in other locations is debated. Hats and coats are still required while doing outdoor activities in cold weather to prevent [[frostbite]] and [[hypothermia]], but the hair on the human body does help to keep the internal temperature regulated. When the body is too cold, the [[arrector pili]] muscles found attached to hair follicles stand up, causing the hair in these follicles to do the same. These hairs then form a heat-trapping layer above the [[Epidermis (zoology)|epidermis]]. This process is formally called [[piloerection]], derived from the Latin words 'pilus' ('hair') and 'erectio' ('rising up'), but is more commonly known as 'having [[goose bumps]]' in English.<ref name="Why Do Humans Get goosebumps When They Are Cold, or under Other Circumstances?: Scientific American.">{{Cite journal|last=Bubenik|first=George A.|date=1 September 2003|title=Why do humans get "goosebumps" when they are cold, or under other circumstances?|url=http://www.scientificamerican.com/article.cfm?id=why-do-humans-get-goosebu|journal=Scientific American|access-date=4 May 2010}}</ref> This is more effective in other mammals whose fur fluffs up to create air pockets between hairs that insulate the body from the cold. The opposite actions occur when the body is too warm; the arrector muscles make the hair lie flat on the skin which allows heat to leave.