Knowing the organs of the human body, where they are, what they do, how they function, and how they interact with one another is the most important factor in becoming a good Sonographer. There is no replacement for this knowledge. You must know the body inside and out, even those organs that Sonographers do not routinely scan. A good Anatomy And Physiology course before starting a program is a great place to begin to get this knowledge. I guarantee that one course in A&P will not even come close to giving you the depth of knowledge that is needed. The human body is so complicated that you will continually learn as long as you scan, but basic understanding will go a long way in preparing you for your new career.