THE RETE TESTIS IN THE ALBINO RAT: ITS STRUCTURE, DEVELOPMENT AND MORPHOLOGICAL SIGNIFICANCE

Abstract

The rete testis was studied in the adult and developing rat by means of dissections, serial histological preparations and reconstructions. The adult rete may be divided into two major parts, an intratesticular portion (with a transitional intratunical part) and an extratesticular portion. The intratesticular portion is largely an elongated slit-like cavity at the cranio-dorsal aspect of the testis immediately underneath the tunica albuginea. The distal segments of the seminiferous tubules as they pass into this part of the rete show peculiar "plugs" of Sertoli cells which are described and discussed. The intratunical part of the rete is a ladder-like network of channels. The extratesticular rete is an irregularly subdivided cavity into which the ductuli efferentes open. The intratesticular rete originates from the gonadal blastema as modified portions of the sex cords. This process is indispensably related to the vascularization of the embryonic gonad. The extratesticular rete arises in the "rete blastema" which probably is of mesonephric derivation. Connections between the meson-ephric tubules and the "rete blastema" are established by the 14th day of fetal life, much earlier than has previously been supposed. Conclusions drawn from the embryological observations are as follows: The intratesticular rete is the homologue of the central canal of the testis, the "Hodenzentralkanal" found in lower vertebrates. It represents the longitudinal anastomosis of the gonadal components (seminiferous tubules, sex cords). The extratesticular rete includes the homologue of a marginal canal of the mesonephros, the "Nierenrandkanal" prominent in sharks. This channel which forms a longitudinal anastomosis between the distal ends of the mesonephric tubules is represented by the "rete blastema". In the rat there is a secondary outgrowth from the sex cords of the gonadal blastema into the "rete blastema" which may replace an uncertain amount of tissue derived from the mesonephros. The findings in the rat point to a unified concept of the mammalian rete and its evolution. The validity of this concept will be established when the development of the mammalian rete in different species has become thoroughly investigated.