Physician assistants are health care professionals licensed to practice medicine with physician supervision. PAs do not have to undertake an internship or residency. Also, a physician has complete responsibility for the care of the patient. PAs share that responsibility with the supervising physicians. The average PA program curriculum runs approximately 26 months. PA students go into the hospital and various clinics to observe and work with experienced doctors and begin to learn how to take care of patients. PA students begin to explore the wide variety of PA career paths, such as family practice, internal medicine, surgery, psychiatry, obstetrics and gynecology, and pediatrics. Because of the close working relationship the PAs have with physicians, PAs are educated in the medical model designed to complement physician training. Upon graduation, physician assistants take a national certification examination.