Question

A long bone is covered externally with a sheath called the __________, whereas the marrow cavity is lined with the __________.

Answer 1

I suggest you to provide some options, as it's quite difficult to answer your question. Here is your answer: A long bone is covered externally with a sheath called the periosteum, whereas the marrow cavity is lined with the endosteum. I've attached the illustration to make it clear for you