Transcript Urogenital Development

Urogenital Development
Table of Contents:
I. Primitive Kidney
II. Internal Genitalia
III. Definitive Kidney
IV. 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
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Removal of the
lateral body wall
Species: Mouse Day Gestation: 9
Approx. Human Age: 28 days View:
Lateral
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. . . 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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