Here is a few occupations in the Biomedical field:
Systems Phisiology engineers look at either an isolated system of the body or cell (e.g. the functions of a human liver), or the processes from the interaction of these isolated systems (e.g. how the nervous system interacts with the heart).
Biomechanical engineer focus on the function and mechanics of the body. The current concentration of research is on tissues and how they heal (aiding orthopaedic and rehabilitaion engineers in their work).
Orthopaedic and rehabilitation engineers could also be considered biomechanical engineers. Orthopaedic engineers are very specific, and only look at how joints function, break, heal, and how to replace them with minimal difference in function. Rehabilitation engineers work in labs or work with patients who are recovering from an injury. They assist in planning and monitoring treatment.