I think the thing that is most concerning to me about this incident is how it ever happened in the first place. Joking around with cadaver body parts is so far out of the realm of acceptable for the overwhelming majority of people, that it would never even occur to them to behave how the OP did. Somehow, he didn't immediately realize that this behavior was wrong and, based on the posts here, he still doesn't seem to understand the magnitude of his mistake. The concerning part isn't just the unprofessionalism, it's the thought process behind it.
I've done rotations with medical examiners and they probably have the sickest senses of humor in all of medicine. They may joke about how a cadaver's tattoos are ironic based on their manner of death, or remark that someone's dentures obviously weren't strong enough to stop a bullet through the palate, but even they would never, never behave as the OP did. Similarly, every physician has probably judged or vented about difficult patients. Every physician copes with stress somehow, but they don't do this. If the OP believes that all of these offenses are the same, that's another (frankly concerning) error in thinking.
OP, it's in your best interest to take full responsibility for your actions. If you get another chance, you need to be aware that your judgment may need some serious work - seek counseling if necessary, but definitely proceed with caution from here on out.