Med school. Anesthesiologist go through medical school and then do at least four more years of training to finish an internship and residency. Nurse anesthetists go through nursing school and then they may apply for a two and a half year training program after working some time as a nurse.
MD vs RN. An anesthesiologist is a doctor who has gone through a residency program and is board certified in anesthesiology. A crna is a registered nurse who has done advanced training beyond nursing school in the area of anesthesia. They also must obtain a board certification. The crna scope of practice is limited and they are supervised by an anesthesiologist.