Why Are Some Curriculars "Extra"?

Three R'sIt’s difficult to question things we don’t realize we assume. For example, few of us ponder why we easily trust our family doctor to diagnose pretty much ANY part of our body, internal or external, except our mouth. Our mouth, it seems, is so darned complicated and unique compared to, say, our aortic valve or epidermal sheath, that only SPECIAL DIFFERENT OTHER TYPES OF DOCTORS can even LOOK at this oral outlier.