There was a rebirth of human anatomical dissection during the middle ages. This occured for a couple of reasons. The first being there was a change in ideology around the body. The ideology shifted towards a belief that the human body and the human soul were two seperate things. So when a person died the soul had no connection to the body after death. This change eliminated the christian religious limitation which had been placed on dissection of humans. The second shift is an increased interest in medicine during this time period. Like during the renaissance there is a increased interest and increased scientific mindset during the end of the medieval period. This allowed for the increased desire to participate in medical endeavors. The third is a shift in ideology around how a cadaver should be handled. During the middle ages it was not uncommon for cadaveres to be dismembered. Nobles and kings even had there bodies  dismembered, saltered, or even boiled after death. This allowed for more access to bodies than had previously been available legally. Due to the resurgence of human dissection in the Middle Ages Leonardo Da Vinci was able to do extensive work with dissection of humans and animals throughout his lifetime. He would use the knowledge he gain during the autopsy for not just anatomical and physiological knowledge, but to more accurately paint human figures.

Source:

Prioreschi, P. “Determinants of the Revival of Dissection of the Human body in the Middle Ages.” Medical Hypotheses 2001.Vol 56 (2):229-234. DOI:https://doi.org/10.1054/mehy.2000.1183. Accessed March 8, 2018