Anatomy and Physiology: Websites

MedlinePlus is the National Institutes of Health's Web site for patients and their families and friends. Produced by the National Library of Medicine, the world’s largest medical library, it brings you information about diseases, conditions, and wellness issues in language you can understand. MedlinePlus offers reliable, up-to-date health information, anytime, anywhere, for free.

One of the most esteemed hospitals in the US, offers a search feature based on symptom.

First published in 1899 as a small reference book for physicians and pharmacists, the Manual grew in size and scope to become one of the most widely used comprehensive medical resources for professionals and consumers. As the Manual evolved, it continually expanded the reach and depth of its offerings to reflect the mission of providing the best medical information of the day to a wide cross-section of users, including medical professionals and students, veterinarians and veterinary students, and consumers

If you need statistics this is the place to look!