The title is my question: what organs are absolutely needed (fatal if injured/removed) by the human body and perhaps animals in general?
I'm not asking which organs are mechanically replaceable, but more what organs cannot be removed (and not replaced) in order to maintain human life.
To clarify the question, I'm wondering what organs when removed (and applied no medical intervention) would cause fatal effects in a short amount of time, or cause semi-fatal effects (ex. shortened lifespan). A list perhaps of importance, if possible, would be nice.
note: I have no medical knowledge so I'll leave 'short' open to interpretation.