20.3 The upper urinary tract: development of the metanephros



Morphologic differentiation of the urinary tract


The ureter anlage and the formation of the evacuating urinary tract


The ureter anlage 14 is an epithelial diverticulum which arises from the caudal portion of the mesonephric duct (Wolffian duct) at the level of the first sacral vertebra. Its enlarged end grows in the dorso-cranial direction and projects into the metanephric blastema.
It is the origin of the intra- and extrarenal excretory passages:

  • Ureter
  • Renal pelvis
  • Major and minor calices
  • Collecting ducts

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Quiz 04


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Quiz 08


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Quiz 09


Fig. 10 - Schematic cut through the kidney (sagittal section) Fig. 11 - Enlargement of the inset
in Fig. 10
 Legenda

1
2
3
4
5
6
7
Ureter
Major calix
Minor calix
Renal pelvis
Collecting duct
Metanephric vesicle
Kidney lobe


8
9
10
11
13
Distal tubule
Proximal tubule
Glomerulus
Connecting tubule
Intermediate tubule

Fig. 10, 11
The branching of the collecting ducts and calices from the renal pelvis is shown. The enlargement in B shows the collecting duct and the various elements that form the nephron.

Meer info

Histological picture of the vessel architecture of the renal cortex


Meer info

Meer information on fig. 11.



The cranial end of the ureter anlage subdivides dichotomically many times due to the inductive effect of the metanephric blastema. Fig. 12 - Development of the
metanephric outflow
 Legenda

1
2
3
2+3
4
5
4+5
Cloaca
Ureter anlage
Metanephric blastema
Metanephros
Mesonephric duct (Wolffian duct)
Nephrogenic cord
Mesonephros

Fig. 12
The renal excretory passages develop from the ureter anlage. This development is described in greater detail in an interactive diagram of region C (see below).


The renal pelvis arises from the swollen end of the ureteric bud 16 that subdivides 4 times over the course of the 4th to 6th weeks. 16 branches arise from this that partially then coalesce again in order to finally form 2 to 4 major calices.
At around the 7th week the minor calices start to develop. They discharge into the major calices. Further dichotomic branching follow - up to the 15th generation (roughly 32 weeks). Thereby the caliber of the tubules is reduced more and more so that finally 1-3 millions collecting ducts are formed in the periphery of the metanephric blastema 18.




Overview of the pictures


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