This is from an anatomical atlas I drew between 2001 and 2003. I was just starting to get serious about art then, and I was having trouble understanding structures in the models I was drawing. So I signed up for gross anatomy at Santa Monica College and spent a couple years drawing from cadavers under their very generous supervision. There were 100 illustrations in the end. They helped a whole lot with back muscles particularly when working from life. I'll post some more of the drawings if you folks find them interesting.