The structure of the epididymis, efferent ductules and ductus deferens of the guinea pig: a light microscope study.

In the guinea pig, the narrow part of the epididymis that traverses the upper pole of the testis and passes downward over the entire length of the gonad is composed exclusively of efferent ductules and the initial segment (zone I) of the epididymal duct. At the beginning of zone II, the narrow contour of zone I expands into a large globular region which lies adjacent to the caudal pole of the testis. The globular region of the guinea pig epididymis is commonly referred to as the cauda epididymidis but in the present study, examination with the light microscope reveals that it is composed of five histologically distinct zones (zones III through VII). A detailed histological analysis of the characteristics of the epithelium in the seven zones of the guinea pig epididymis and in the efferent ductules and ductus deferens was udertaken to obtain a better understanding of structure-function relationships in the epididymis of the guinea pig. It was found that each of the zones could be readily distinguished on the basis of its histological features and primarily on the basis of the appearance of the principal cells.