We often use the definite article with professions even though we are not referring to a specific individual:
"The pipes are leaking -- I'd better call the plumber."
"You look really sick. You ought to see the doctor right away!"
... and so on.
Is this a BrE AmE difference?The plumber and the doctor imply that the speaker, or the listener, has one specific "definite" regular plumber and doctor.
The doctor is simply a metaphor for sickness. Translating we get "An apple a day keeps sickness away.." Be it a true, or a false statement.Why do they say THE doctor here? They don't mean any doctor in particular. May be they refer to a category of professions?
On the other hand, you would get THE closest nurse, or one of THE nurses currently on duty in that ward/floor, or THE nurse who comes when you yell "Nurse!". You wouldn't walk past all those nurses, get in your car, drive to a random town, and start looking for A totally non-specific nurse.If I were in a hospital room and the person I was visiting suddenly took a turn for the worse I might say: "Get the nurse". I might not know any particular nurse and I wouldn't be referring to a specific nurse.