Just look at what matters to you. For example, I am fascinated with both the blood and cancer metastasis, so I plan to specialize in hematology-oncology with my medical degree. On the graduate side, I will focus more on the laboratory, not the department. This is really important!!!
For example, I work in a cell/molecular lab right now, but I'm a bioengineer who is applying bioengineering principles to bone tissue.. and there is another BioE in my lab too. The others include those in the CMB program. In other words, think about what you like, and the applications to medicine will arise from your lab of choice!
Don't fret too much about this right now. You will do lab rotations, I believe, in the first 2 years of medical school. Many don't require you to join a department or lab until year 3 (G1, after M2).
😀 Less stress will go a long way. 😀