Who cleans up the blood after a serious auto accident? How do junkyards prep vehicles on their lot?

My husband made a trip to the junkyard today, looking for a cheap part for his truck. He observed that, although many of the vehicles in the yard had obviously been in wrecks or some that appeared to have been cut open with the jaws of life – that none of the vehicles had so much as a hint of blood. He noticed, after seeing a spot where it appeared that someone’s head had hit the windshield, but that there wasn’t a trace of blood anywhere in the car, and so he started paying closer attention.

It would make sense that there be some type of protocol for cleaning up blood after an accident, but who does that? Do they only clean up the scene of the incident, or do they also clean up hazardous material within the vehicle itself?

Do junkyards have a cleaning process for cars that come in?

Is the car cleaned of biological material in the case of a very serious, or fatal car accident (assuming that, in some situations, there would be more than just blood, like digits or lots of tissue, even brain matter, urine, feces)? Who does that?

Are there any other precautions that junkyards take when bringing in new cars, or are they basically just loaded onto the lot and left there?