what gets submitted first

ok so i have completed everything necessary to submit to insurance for approval but when i talked to my surgeons office they said they just sent my letters of medical necessity to my pcp and to wait a day or 2 then call my pcp. i thought letter of medical necessity went straight to insurance can anyone explain this process to me i was hoping to hear sumthing from insur soon but now it seems like its gonna take atleast a cpl weeks... oh btw i have healthnet hmo