What three general functions do nutrients perform in the body?

Well you eat healthy food through your mouth. Pretty much Digestion is how the body get nutrients.

Your saliva starts it, stomach breaks food down (Think like a blender) as well as killing some bad bacteria. Then the small intestine breaks it down even more so the body can absorb the nutrients, vitamins, protein etc..

So it's the small intestine that the body uses to get nutrients. But it's a big process. If you want more detailed info google is your friend just search "digestion nutrition" without quotes