Answer:
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.
What is that you will break everytime you name it?
Twigs and spheres and poles and plates. Join and bind to reason make.
What I am filled, I can point the way. When I am empty. Nothing moves me. I have two skins. One without and one within.
What is lengthened by being cut at both ends?
A leathery snake, with a stinging bite. I'll stay coiled up, unless I must fight.