The human body is an amazing organism.
So we incubate for ten months - and during that time develop a heart, lungs, bones and muscles. And what we have developed can last us until age 60, 80 or 110. I don't think about it very often (the concept of a heart beating for 95 years) because if I did my head would hurt.
Someone I know (my father in law) has now had a pacemaker AND a new hip put in, in the span of a year. Thankfully, not at the same time, but within a few months of one another.
Funny how we don't really think about those things (our hearts beating regularly or hip joints moving) until they stop working. It's also fairly awe-inspiring that we know enough to be able to treat these problems - so people don't have to live in pain (or as invalids) as they get older. No wonder the life expectancy isn't age fifty any longer.