Histological Division of Mouse Epididymis Based on Regional Differences

We divided the mouse epididymis into 5 segments (Segments I-V) based on regional diff erences in histology to obtain a fundamental division that refl ects the functions of this organ. Segments I-III are contained in the caput epididymidis, Segment IV in the corpus epididymidis, and Segment V in the cauda epididymidis. For this classifi cation, we observed morphological features of the epididymal duct in adult mice by light and electron microscopy, and examined postnatal development of the epididymal duct qualitatively and quantitatively. We also performed experimental studies to examine the eff ects of ligation/cutting of the eff erent ducts, epididymal duct ligation at the border between Segments III-IV, testis irradiation, cryptorchidism, and estrogen administration on epididymis histology. In these studies, we found that the epididymal duct in each segment responds as a functional unit when the epididymis is subjected to pathological conditions. In conclusion, the present histological division is useful as a basic division for studies on the mouse epididymis. Hirosaki Med.J. 59, Supplement:S292―S301,2007