apparently...

The longest strand of hair on the human body is actually the eyebrow. The hair on the eyebrow is connected to the brow ridge which goes under the skin and it travels down the human body under the epithelial tissues in parallel to the spine. That hair finally exits at the surrounding area of the anus which most french scientists call "le butt hair". That is why every time you pull your butt hair, your eyebrow will twitch