|Bone. It's hard, one the hardest
components of the human body. Yet it's still got a bendy component, which
is a good, because if it didn't we'd all be crumpled heaps on the floor.
Also despite its hardness, bone has got a gentle, caring side. It protects
all the internal organs, allowing us to crash into things on occasions without
too many repercussions. It's also useful in that it allows us to do things
like walking, talking and well just about everything really. Imagine life
as a jellyfish, it can't be fun.
Bone is in fact living tissue, so it needs a blood supply. If you do the right things to fresh bone (namely strip away an outer layer called the periosteum, but that's getting gorey) it you can see it bleed. This living component of bone is the bendy bit. While the hard, brittle bit, is made of a mineral called hydroxyapatite.
Some weird things start happening to bones, if you take them into space,
or if you put to much strain on them through exercise, or simply as you
age. Lots of research goes on about bones in these conditions and ways
of keeping bones healthy