Belching the vapours of musk means that after meals one would not feel heaviness and acidity. On the other hand, the belch will give out scented air, and the food will be digested by it. There will be no excrement or urine there.
Secondly, recitation of Allah's Name will ever remain on their tongues without the least effort like the way we breathe, without any effort whatsoever. In other words the food in Jannah would be so light and fine that there would be no disagreeable urine excrement. On the other hand, there will only be fine smell like that of musk.