I used to do cadaver dissection in college. The remains of any particular person were very carefully kept together and separate from others. The medical school to which the remains were originally donated had them cremated and returned to the families of the deceased.
My only caution would be to avoid donating to an institution that does not dispose of remains properly. UC San Francisco, for instance, says:
After studies are completed the remains are cremated and scattered at sea. Frequently Asked Questions | UCSF Medical Education
The Catholic Church allows burial of cremated remains at sea, but only if the ashes are buried together. Ashes may not be scattered, no matter where this is done.
In contrast, Oregon Health and Science University says:
Studies are usually completed within two years. After that time, the process of cremation and return of the cremains (cremated remains) to the donor family is undertaken. Body Donation | OHSU
