Which bone is the Sternum? Sorry, I just suck at Biology...

Anyway, I'm thirteen and never broken a bone. Even though I've jumped off a shed roof and onto a bed matress (only sprained my ankle), got knocked down by a car on a very big hill (just got deep scratches and cuts), and I'm sure I could think of quite a few.
And still I've never broken a bone. But I kinda wanna break my arm. I've always wanted a cast.

__________________