I am assuming if the are broke they won't fire at all or if they did they would be unsafe?
You're correct, unsafe. They will fire alright, but can also fire too easily and when not expecting it. A worn or broken sear can slip off the full cock notch which doesn't break.
Or if either the safety or loading notch are broken, even a good sear may catch but slip off at any time with enough force for the gun to go off even from the safety position.
Easy to tell if either sear or the 1st two notches are broken: If notches are good, once you hear the click at either of the 1st two notches and release the hammer, it will move forward about 1/8" as the sear seats into the bottom of the notch pocket. If it clicks and the hammer stays right there, something is amiss.