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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.
The mesonephric duct, also known as the Wolffian duct, archinephric duct, Leydig's duct or nephric duct, is a paired organ that develops in the early stages of embryonic development in humans and other mammals. It is an important structure that plays a critical role in the formation of male reproductive organs.
[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 ]
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.
Each metanephric kidney is characterized by a large number of nephrons and a highly branched system of collecting tubules and ducts, [28] that open into the ureter. [48] Such branching in the metanephros is unique in relation to the pronephros and mesonephros. [ 44 ]
The collecting duct system of the kidney consists of a series of tubules and ducts that physically connect nephrons to a minor calyx or directly to the renal pelvis.The collecting duct participates in electrolyte and fluid balance through reabsorption and excretion, processes regulated by the hormones aldosterone and vasopressin (antidiuretic hormone).
The mechanism of multicystic dysplastic kidney is a result of an abnormal induction of metanephric mesenchyme. This could be a result of a formation difficulty of the mesonephric duct . Some mutations in genes associated with renal dysplasia (in syndromes) have been determined.