urogenital development
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Urogenital Development
Table of Contents:
I. Primitive KidneyII. Internal GenitaliaIII. Definitive KidneyIV. External Genitalia
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Both the urinary and
genital components of the urogenital
system are derived, to a large extent,
from the intermediate mesoderm.
Species: Mouse Day Gestation: 8 Approx. Human Age: 22 days View: Transverse Cut
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The intermediate mesoderm becomes
segmented into units termed nephrotomes.
The lateral portions of the nephrotomes
unite, forming a longitudinal duct
on each side of the embryo
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The lumen of each nephrotome opens into the mesonephric duct as well as into the
body cavity. Glomeruli form as small vessels extend from the dorsal aortae.
Human Age: 27 days http://www.visembryo.com/baby/index.html
Removal of the lateral body wall
Species: Mouse Day Gestation: 9 Approx. Human Age: 28 days View: Lateral http://www.visembryo.com/baby/index.html
. . . illustrates the mesonephric duct
extending toward the cloacal region and the
openings of the nephric tubules into the body
cavity.
Species: Mouse Day Gestation: 9 Approx. Human Age: 28 days
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As development progresses, the nephrogenic tissues forms
urogenital ridges on the dorsal wall of the body cavity. The boxed area at higher magnification . . .
Species: Mouse Day Gestation: 10-11 Approx. Human Age: 5-6 weeks View: Transverse Cut
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. . . illustrates the mesonephric duct, the nephrotome, and the mesoderm
covering the urogenital ridge.
Species: Mouse Day Gestation: 10 Approx. Human Age: 5 weeks View: Transverse Cut
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The urogenital ridge consists of the mesonephros and the gonad.
The mesonephros consists of excretory tubules that contact a blood vessel medially and enter the
mesonephric (Wolffian) duct laterally. At higher magnification . . .
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. . . the relationships of the glomerular vessel, the duct and mesonephric tissue are seen.
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The gonads develop as primordial germ cells that form in the wall of the yolk sac close to the allantois migrate along the
dorsal mesentery of the hindgut to invade the genital ridges.
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The path of germ cell migration within the dorsal mesentery is shown on this micrograph.
Species: Mouse Day Gestation: 11 Approx. Human Age: 6 weeks View: Transverse Cut
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The primordial germ cells become surrounded by cells of the primitive sex cords. At this stage the gonad is "indifferent," as one cannot morphologically distinguish between the male and female.
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