1. Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
2. Department of Gastrointestinal Surgery, Xiantao First People's Hospital Affiliated to Yangtze University, Xiantao, Hubei 433000, P.R. China
3. The Medical Laboratory Center of General Hospital of Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China