My body

[Panic Button]

My skin is constantly being replaced, and presumably so are all the fleshy parts of my body. What you see of me is not what you saw a year ago, except my teeth.

I feel like the same person but how much of my body is made up of the same molecules as when I was young.

Are my bones constant, or are they replaced? (They heal if broken so laying down new bone tissue is possible).

I believe I can't manufacture new brain cells, but are the molecules that constitute them replaced?

I guess almost my entire body is changed many times over.

[stevie21]

As a kid, millions of new neurons are still forming - it's only as an adult that there's less "neurogenesis" (new neurons being formed). Less, rather than none. On the whole I'd guess that an adult brain is made of the same neurons/molecules today that it will be in a decade. The neurotransmitters and all the blood & fluids would be newly generated though.

Beyond that I have no idea if any part of your body is completely static. Are adult, uninjured bones always made of the same molecules or is there constant regeneration there as there more obviously is with hair?