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Rock hyrax at San Diego Zoo. | |
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Rock hyrax female with young at San Diego Zoo. | |
2)
General Gestational Data Since this original description two placentas have become available and they were weighed. The first comes from a stillborn female fetus (317 g) in which the placenta encircled the mature fetus as shown next. The placenta weighed 19 g and measured 16 x 3 cm; it was 0.3 cm thick, uniformly so. The second placenta was from a term live born and weighed 25.6 g, measuring5.5 x 5.5 x 0.3 cm. The umbilical cords were short and split into their major vessels.
3)
Implantation |
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Hyrax placenta of quadruplets, two (bottom) with maceration. Note the ring-shaped (zonary) type of the disks. At the red arrows are the cord insertions. | |
4)
General Characterization of the Placenta |
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The three layers of a nearly mature hyrax placenta, as described by Wislocki & v.d. Westhuysen (1940). | |
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The two stillborn hyrax fetuses (107 and 93 g) of the placenta shown first. The macerated fetuses (two of quadruplets) are shown in the section on Pathology. | |
5)
Details of fetal/maternal barrier |
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Border of zones I (above) and II (below left) | |
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Surface portion of zone I with large maternal blood sinuses beneath the chorionic plate and mesenchyme streaming from the chorion into the villi. These are covered with dark trophoblast, largely empty spaces are maternal sinusoids. | |
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Section through the trabecular labyrinth with mesenchyme of villi (F) and maternal blood (M). The cellular trophoblastic surface is somewhat autolyzed in this post mortem specimen. It has been variably interpreted as syncytium or cellular trophoblast. | |
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Another view of the villi (trabeculae) and maternal blood in between. | |
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Zone III with large maternal artery (Wislocki & v.d. Westhuysen considered this to be a vein) infiltrated by trophoblast. Beneath is the degenerating decidua. | |
6)
Umbilical cord
7)
Uteroplacental circulation
8)
Extraplacental membranes |
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Mesenchymal nodule on amnionic surface. | |
9)
Trophoblast external to barrier
10)
Endometrium |
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Floor of the placenta with maternal artery that is surrounded by the large "epithelioid cells" described in the text (? trophoblast). Note the foci of dark blue calcification and, at bottom right, the compacted, degenerating decidua. | |
11)
Various features
12)
Endocrinology
13)
Genetics
15)
Pathological features |
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Two macerated fetuses of quadruplets discussed in text. These were presumed to be monozygotic twins because of the presence of only three corpora lutea in a quadruplet gestation. | |
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Histologic appearance of the placenta shown above, from the macerated fetuses showing massively dilated maternal blood channels and collapsed fetal surface vessels. | |
16)
Physiologic data
18)
Other remarks - What additional information is needed?
Acknowledgement
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