The other, more superficial, portion of the diverticulum, on the other hand, potenspiller becomes the ureter. The ureter opens at first into the hind-end of the Wolffian duct; after the sixth week it separates from the Wolffian duct, and opens independently into the part of the cloaca which ultimately becomes the urinary bladder. In the outer part of the intermediate mesoderm, immediately under the ectoderm, in the region from the fifth cervical segment to the third thoracic segment, a series of short evaginations from each segment grows dorsally and extends caudally, fusing successively from before backward to form the pronephric duct. The ureteric bud subsequently grows into the latter mass, forming the parts of the nephron. One end grows toward and finally opens into the Wolffian duct, the other dilates and is invaginated by a tuft of capillary bloodvessels to form a glomerulus. Each kidney originates as a ureteric bud from the caudal end of the Wolffian duct, which, in turn, originates from intermediate mesoderm.
Other changes include e.g. the translocation of the ureteric opening directly into the cloaca. In the female, on the other hand, the Wolffian bodies and ducts atrophy, leaving behind only remnants in the adult, involving e.g. the development of the suspensory ligament of the ovary. There are also developments of other tissues from the mesonephric duct that persist, e.g. the development of the suspensory ligament of the ovary. Each arises on the lateral aspect of the corresponding mesonephric duct as a tubular invagination of the cells lining the abdominal cavity. Each arises on the lateral aspect of the corresponding Wolffian duct as a tubular invagination of the cells lining the abdominal cavity. The abdominal opening of the left uterine tube. The orifice of the invagination remains open, and undergoes enlargement and modification to form the abdominal ostium of the fallopian tube. The original evaginations form a series of transverse tubules each of which communicates by means of a funnel-shaped ciliated opening with the abdominal cavity, and in the course of each duct a glomerulus also is developed.
Thus, the mesonephric duct remains after the atrophy of the pronephros duct. The mesonephric duct originates from a part of the pronephric duct. It absorbs the ends of the Wolffian ducts and the associated ends of the renal diverticula, and these give rise to the trigone of urinary bladder and part of the prostatic urethra. In the other end, the renal tubules give rise to Bowman’s capsules and glomeruli. The paramesonephric duct gives rise to the female fallopian tubes, uterus, cervix, and upper part of the vagina. Shortly after the formation of the mesonephric ducts, a second pair of ducts is developed; these are the paramesonephric ducts. The mesonephric ducts end in an epithelial elevation, the sinus tubercle, on the ventral part of the cloaca between the orifices of the mesonephric ducts. The definitive urogenital sinus consists of a caudal phallic portion and an intermediate narrow channel, the pelvic portion. At a later stage the sinus tubercle opens in the middle, connecting the paramesonephric ducts with the cloaca. This fusion of the paramesonephric ducts begins in the third month, and the septum formed by their fused medial walls disappears from below upward.
Around the fifth month, a ring-like constriction marks the position of the cervix of the uterus, and after the sixth month, the walls of the uterus begin to thicken. Their exact position may resemble her posture during the last few weeks in the uterus. The portions which lie in the genital cord fuse to form the uterus and vagina. The parts outside this cord remain separate, and each forms the corresponding fallopian tube. Instead, the tubules rapidly elongate to form the parts of the nephron: the proximal tubules, the loops of Henle and the distal convoluted tubules. On the medial side of the Wolffian duct, from the sixth cervical to the third lumbar segments, a series of tubules, the Wolffian tubules, develops. In the male, the Wolffian duct persists, and forms for example the epididymis, the ductus deferens, the ejaculatory duct, seminal vesicle and efferent ducts. In the male, the duct persists, and forms the tube of the epididymis, the vas deferens and the ejaculatory duct, while the seminal vesicle arises during the third month as a lateral diverticulum from its hinder end. The ducts pass backward lateral to the Wolffian ducts, but toward the posterior end of the embryo they cross to the medial side of these ducts, and thus come to lie side by side between and behind the latter-the four ducts forming what is termed the common genital cord, to distinguish it from the genital cords of the germinal epithelium seen later in this article.