The primary duty of any Medical Officer is to provide for the health and well being of his or her Ship, Crew, and Captain. As a Doctor, one is required to render aid to anyone in any situation. They have jurisdiction over any medically hazardous or medically necessary situation, making sure that it can not endanger the ship. Because of this directive, it may be necessary for one to leave the ship in order to provide care. It becomes their responsibility to enter any situation that may endanger the lives of other crew members, be it disease, bio-contamination, or plague.
Doctors are responsible for the bio-hazard protocols on your ship, and for the monitoring of the transport biofilters. Any medical care that is needed, be it a small bruise or abrasion, or full scale cardiac surgery becomes their responsibility. Aboard a starship, Medical officers report directly under the Chief Medical Officer