My immediate question after reading this post is how would this PS tell the reader much about you as a person? You want your PS to illustrate 1. why medicine and 2. why you. Writing an analytical essay about the problems of the healthcare field (which is what this sounds like to me) is not really what a PS is about. Do you have personal experiences working with underserved populations that you're going to write about? Maybe focus on that instead? You'll also want to suggest to the reader why you're interested in medicine as opposed to, say, public health or policy.