Fine structure of the canine prostatic complex.

The canine prostatic complex, including the prostatic urethra, the urethral openings of the prostatic gland ducts, the prostate gland proper and the ejaculatory ducts has been studied with the transmission and scanning electron microscopes. The urethral epithelium was found to be a modified transitional epithelium; it extended a short distance from the urethra into the orifices of the ducts where it gradually lost height. The columnar cells were replaced by cuboidal superficial cells in the terminal ducts of the gland. With increasing distance from the urethral openings of the ducts, the superficial cuboidal cells developed secretory activity and finally were indistinguishable from regular prostatic secretory cells. The latter formed typical prostatic acini, consisting of secretory cells which were merocrine in nature, and flat lentilate basal cells. In addition to exocrine cells, three different types of presumptive endocrine cells occurred, predominantly in the periurethral ducts of the prostate gland. It has been concluded from this study that, firstly, fluid absorption and spermatophagy are the main functions of the epithelia of the ejaculatory ducts and the ampulla of the vas deferens. Secondly, it has been concluded that the different functions of the various structures of the prostatic complex can be related to their different embryological origins.