An operating room is a sterile environment in which germs cannot be introduced. Doctors and nurses do something called scrubbing in when they are entering an operating room. This means that they scrub their hands and arms and are then fitted with sterile gowns and gloves so that they do not introduce any germs into the environment. Food and drinks are strictly prohibited in such an environment as they might introduce germs or toxins that could result very badly for the person being operated on.
In an operating room people’s insides are being exposed while they have whatever procedure done that they are having done.