University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

343

Pages:

2
Author:

Mariam A.

Basic principles of in utero renal and urogenital tract development    The urinary tract develops from the 3rd week of the embryonic period from the intermediate mesoderm (kidneys and the kidney ducts) Kidney development – nephrogenesis, describes the embryologic origins of the kidney, a major organ in the urinary system. Three slightly overlapping kidney systems are formed in a cranial-to-caudal sequence during intrauterine life in humans: the pronephros, mesonephros, and metanephros. The first of these systems is rudimentary and nonfunctional; the second may function for a short time during the early fetal period; the third forms the permanent kidney. o Pronephros = first kidney formed and is non-functional. Most superior in position and persists from 4th week to 6th week o Mesonephros = second kidney and is functional only in embryo. Intermediate position. Early in the fourth week of development, during regression of the pronephric system, the first excretory tubules of the mesonephros appear. They lengthen rapidly, form an S-shaped loop, and acquire a tuft of capillaries that will form a glomerulus at their medial extremity o Metanephros = final kidney formed and is functional in fetus and adult. Most inferior in position. The ureter is the duct that drains urine from the metanephros. The ureters and collecting duct system of the kidneys differentiate from the ureteric bud; the nephrons differentiate from the metanephric blastema. The number of nephrons formed ultimately depends on growth and branching of the ureteric bud, formation of mesenchymal condensations and the conversion to epithelial tubules The metanephros is formed in the sacral region – level of the first sacral vertebra (S1) and bifurcation of aorta. In the adult, the kidney lies at the upper lumbar level   ‘Migration’ of kidney occurs between the 6th and 9th week and the kidneys finally come to lie at the level of the 12th thoracal vertebra (T12) under the suprarenal glands. Note that as the kidneys “ascend”, they are supplied by arteries at successively higher levels