If you don't look where you're going, you could bash a knee, or bark your shin, or bang your elbow. But stubbing your toe will bring tears to your eyes, and may hurt for quite some time afterward. Why is this so painful? At Marquette magazine, the answer comes from Chris Geiser, clinical assistant professor of exercise science and director of Marquette's athletic training program.

"First, our feet and hands are our interface to the world. As such, they are highly innervated with nerve endings that provide sensory feedback to our central nervous system, which uses this information to guide our actions. With our toes and feet, this is as simple as sensing the shape of the ground, the incline, the pressure that our shoes create on our feet, or the slipperiness of the surface we are standing on — all very important information if we are to successfully navigate our world.

That's just the beginning of the explanation, so read the rest at the college's site. Link -via Metafilter