1. Department of Anatomy, Basic Medical College of Weifang Medical University, Weifang, Shandong 261053, P.R. China
2. General Surgery Department, Shandong Provincial Qianfoshan Hospital, Jinan, Shandong 250013, P.R. China
3. Morphology Laboratory, Basic Medical College of Weifang Medical University, Weifang, Shandong 261053, P.R. China