You are probably wondering, why should I care about this?

Well, it makes a great target for male contraception. This spinny bit is the only spinny bit in humans. The problem with male contraception meds is that most of them really fuck with your desire to have sex in the first place -- it's a problem a lot of meds have, seeing as how nature re-uses bits over and over in the body, inadvertently hitting something else -- but this, this is a great target to hit.