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The metanephrogenic blastema or metanephric blastema (or metanephric mesenchyme, or metanephric mesoderm) is one of the two embryological structures that give rise to the kidney, the other being the ureteric bud. The metanephric blastema mostly develops into nephrons, but can also form parts of the collecting duct system.
Ectopic ureter (or ureteral ectopia) is a medical condition where the ureter, rather than terminating at the urinary bladder, terminates at a different site. [1] [2] In males this site is usually the urethra, in females this is usually the urethra or vagina. [3]
The elongated stalk of the ureteric bud, called the metanephric duct, later forms the ureter. As the cranial end of the bud extends into the intermediate mesoderm, it undergoes a series of branchings to form the collecting duct system of the kidney. It also forms the major and minor calyces and the renal pelvis.
By about 20 weeks, the ureteric bud has formed the ureters, the renal calyces, collecting ducts, and collecting tubules, while the metanephric blastema develops into the nephron itself, which includes the epithelial cells and the podocytes of Bowman’s capsule. In the third trimester and throughout infancy, the kidneys continue to grow and mature.
[17] [6] [18] Differences in kidney structure are the result of adaptations during evolution to variations in body mass and habitats (in particular, aridity) between species. [ 19 ] [ 20 ] [ 12 ] The cortex and medulla of the kidney contain nephrons , [ 21 ] each of which consists of a glomerulus and a complex tubular system. [ 22 ]
Metanephric adenoma (MA) is a rare, benign tumour of the kidney, that can have a microscopic appearance similar to a nephroblastoma (Wilms tumours), [1] or a papillary renal cell carcinoma. It should not be confused with the pathologically unrelated, yet similar sounding, mesonephric adenoma .
Metanephric dysplastic hematoma of the sacral region (MDHSR) has been described by Cozzutto and Lazzaroni-Fossati in 1980, [1] by Posalaki et al. in 1981 [2] and by Cozzutto et al. in 1982. [3] Three additional cases were seen by Finegold.
During early development (approximately day 22 in humans), the pronephric duct forms from the intermediate mesoderm, ventral to the anterior somites. The cells of the pronephric duct migrate caudally whilst inducing adjacent mesenchyme to form the tubules of the initial kidney-like structure called the pronephros. [6]