 | Figure 2
Nature Genetics
25, 248 - 250 (2000)
doi:10.1038/76985
The labyrinthine placentaJulie Rinkenberger
& Zena Werb | | | | Figure 2. Development of the mouse (a−c) and human (d−f) placenta.
a, At E10.5, the labyrinth forms. Maternal vessels are indicated in red, and fetal vessels, in light blue. b, The fetal vessels from allantoic mesoderm penetrate the chorion and invade the labyrinth. Syncytiotrophoblast (indicated in purple) forms around the developing fetal vessels. Maternal blood sinuses also enter the labyrinth and supply blood to the fetal vessels across the syncytiotrophoblast barrier. c, Trophoblast stem cells from the chorion express Gcm1 at the developing tips of the branching epithelium. Fetal mesenchyme containing vessel precursors undergoes branching morphogenesis and invasion behind the trophoblast layer. The invading trophoblasts will become the syncytiotrophoblast barrier between maternal blood sinuses and fetal blood vessels. d, Human placenta showing fetal villi and umbilical cord with fetal vessels in villi. Villi are bathed in maternal blood, which exits through the maternal veins. A syncytiotrophoblast sheath around the villi prevents direct contact between maternal and fetal blood. e, Two fetal villus trees illustrate the complex branching pattern. Each villus branch is also covered with branched microvilli (not shown) and surrounded by syncytiotrophoblast (indicated in purple). f, Each villus, depicted in cross section, is bound by a syncytiotrophoblast layer and bathed in maternal blood. Inside the villus is a layer of cytotrophoblast and the basement membrane. The central part of the villus contains fetal mesenchyme and vessels.
Bob Crimi |
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