How do I arrange it so that my body is donated to scientific research after my death?

I’m having trouble wording the question so that it’s clear I mean making the arrangements now, not after I’m dead. But I’d like to make such arrangements. Go to a funeral director and it can easily end up costing my estate $10,000 or more, money my survivors can certainly find a better use for. I’d feel much better knowing that instead of a costly burial taking money from my heirs, my demise might actually do them some good should medical science learn a bit about how to mitigate whatever ends up doing me in.