Developmental studies on the kidneys of rabbits

ABSTRACT

The development of the rabbit's kidney was investigated during the pre and postnatal periods. The bilateral mesonephroi appeared in 11 days old fetuses as two masses bulging into the coelomic cavity; one on either side of the developing aorta. Each mesonephric blastema was composed of primitive tubules, corpuscle and duct; supported by vascularized mesenchyme and covered by the coelomic mesothelium. By the 14[th] day, brush border appeared in some mesonephric tubules. Once the metanephroi appeared; in 15 days old fetuses, degenerative changes began to occur in the mesonephroi. The latter were completely disappeared in fetuses of 22 days of age. In 15 days old fetuses, the uretric bud appeared in the center of the metanephric blastema. As the fetal age reached 17 days, this bud began to branch. At 20 days, metanephric corpuscles started to develop. Near the end of fetal life, marked maturation of some corpuscles was evident. By the 25[th] day, the proximal and distal tubules as well as the macula densa began to appear. In 27 days old, the renal pelvis, collecting tubules and the medullary rays became visible. Moreover, thick and thin segments of nephrons loop appeared in the medulla. In newly born rabbits, the production of new nephrons in the subcapsular zone persisted for 2 weeks. From 4 weeks and onward, the collecting tubules became lined by dark and light cells