1. Department of Histology and Embryology , Poznań University of Medical Sciences , Poznań , Poland
2. Department of Infectious Diseases, Hepatology and Acquired Immunodeficiency , Poznań University of Medical Sciences , Poland
3. Department of Anatomy and Histology, Collegium Medicum , University of Zielona Góra , Zielona Góra , Poland
4. Division of Histology and Embryology, Department of Human Morphology and Embryology , Wrocław Medical University , Wrocław , Poland