I intended to post an article on embryology of the kidney. This article just made it easier.
Pronephros draining from the coelom into the pronephric ducts (approximately day 22 of gestation)
Mesonephros draining directly from capillaries into mesonephric (wolffian) ducts: this system is similar to that of aquatic amphibians and fish
Metanephros draining from capillaries into bowman’s capsules and renal tubules (approximatesly by 5th week) and then into metnephric duct that later forms ureters.
While the metanephric ducts travel caudally to join the bladder as ureters, the metanephri rotate and migrate upwards as the torso elongates during development of fetus. this elongates the ureters.
At the end of formation of fully functional kidneys which is by 32- 36 weeks, there are one million nephrons.