My daughter wanted to study anatomy in 5th grade. I had 2 little ones to homeschool also, and couldn't add another science curriculum into my schedule. Apologia Anatomy and Physiology was the perfect fit. I did get her the CD that reads the book, mostly for pronunciation of the unfamiliar technical words. She loved the Notebook (from Apologia that coordinates with the book), and finished the course in only 5 and a half months. One day towards the end of the course she was at a doctor's office for a broken bone. The doctor started quizzing her on bones and muscles, and she picked up the model he had and talked for 5 minutes about bones, joints, muscles, blood, etc. He was floored!
I highly recommend this curriculum to students ready for a more intense, formal science unit.