the point is: that is not a picture of a proton, it's a schematic rappresentation. You can see it as a Euler diagram that says that in the proton you have 3 valence quark and some glouns.

by the way what are the exact constituents of the proton is still an open question.

The point is, that is not a picture of a proton; it's a schematic representation. You can see it as a Euler diagram that says that in the proton you have 3 valence quarks and some gluons.

By the way the exact constituents of a proton is still an open question.