It may help a bit to take classes like Anatomy, Physio and Biochem in undergrad. Any prior exposure is helpful. That said, I took only the bare requirements and have a pretty good GPA. Plenty of people who took those courses struggled, so while it's helpful I don't think it's necessary by any means. As far as Anatomy is concerned, the level of detail you'll be going into far exceeds the rigor of whatever you learned in undergrad anyways.