In the traditional dental / medical school, students go through separate classes covering Biochemistry, Genetics, Gross Anatomy, Histology, Immunology, Microbiology, Neuroscience, Pathology, Physiology, Pharmacology, etc.
In the schools that use system-based learning, all of the abovementioned courses (and more) are integrated together in the study of the major systems of the body (i.e. Blood and Lymph, Cardiovascular, Endocrine, Gastrointestinal, Musculoskeletal, Nervous, Renal, Reproductive, Respiratory, Skin).
Under SBL, rather than learning about the individual "pieces" of human biology, you're essentially learning how the pieces fit together ...