Estrogen-Induced Cryptorchidism in Animals

Abstract

Ontogenesis of the genital apparatus of the mouse shows a repetition of some phylogenetic stages (Figure 1). At the eleventh day of gestation, the gonads are situated in the urogenital anlage. By the thirteenth day this is clearly distinguished from the mesonephros. The gubernaculum extends from the caudal pole of the mesonephros to the inguinal region, where it terminates in a small prominence. The testis is held dorsolaterally by the mesonephros for its entire length and the gonad appears to be embedded in the mesonephros. By the fifteenth day the gubernaculum has become larger. The cranial pole derives from the mesonephros and its caudal pole is attached by a funnel-shaped formation to the inguinal region. The cranio-caudal differentiation of the mesonephros develops further in a caudal direction. The ligamentum diaphragmale is still present, but more elongated and lying against the dorsal abdominal wall. The transabdominal movement of the testis occurs as early as the seventeenth day of gestation, when the gubernaculum changes its shape and is pushed against the lower abdominal wall. The caudal pole of the mesonephros becomes somewhat smaller, because the ductus deferens has separated from the mesonephros. The epididymis has more coils.