The picture is a cross section of a bone. which structures of the bone are indicated by the arrows? x-compact; y-spongy x-spongy; y-marrow x-spongy; y-compact x-marrow; y-spongy

Ihave a really high metabolism and only weigh 70 pounds (13 almost 14). people always ask me two questions: do you ever eat and how do you eat so much and stay so skinny.i am worried that a high metabolism wont me forever. what are some safe steps i can take to maintain being fit. (also, i already work out i am a dacer so i get cardio a lot)