So, what are we?

So the other day I was on Facebook and saw the old Kool-Aid Man meme - is he the liquid or the jar?  I thought about it for a minute, but then moved on without too much mental energy lost - doesn't really matter to me either way.  Then the other night, after my shower, I was noticing all the hair on the floor (and walls) in my bathroom and I started thinking about how our bodies renew themselves. This brought me back to the underlying question attached to the Kool-Aid Man question, are we, as humans, our body, our mind, our spirit?  If we are our bodies, but our bodies renew themselves, what are we really?  Does any part of us remain constant throughout our whole lives?  This took more mental energy.

I did a little (very little actually) looking on the internet, and found out that there are just a few things that we carry with us for our entire lives without them being replaces.  It seems that materially, we are our central nervous system, our tooth enamel, and our eye lenses.  If you happen to be female, you don't get more eggs either.  Even our heart muscle, which was once thought to be permanent actually slowly replaces itself over time. Since a person can live without there teeth or without eggs, and science can now replace the lenses in our eyes, it seems that we are basically our central nervous system.  Maybe that means that we are our minds, after all.  Everything else is like George Washington's axe, we've had to replace the head and the handle a few times.  I find that kinda interesting.  Okay, that's all, carry on.