Figure 3

Placentation in the capybara at around 70 days of gestation. (A) Schematic drawing showing the thin capsular decidua, visceral yolk sac, amnion, main placenta, subplacenta and basal decidua. (B) The capsular decidua has been opened and reflected to expose the fetal membranes. The amnion has also been cut open but retains its attachment to the surface of the chorioallantoic placenta (arrowhead). The visceral yolk sac is inserted more peripherally (arrow). The yolk sac vessels terminate in the sinus terminalis (asterisk). (C) At this stage the lobes of labyrinth are clearly separated by interlobar areas. This view also shows the relation between the visceral and parietal parts of the yolk sac, the fibrovascular ring and the margin of the chorioallantoic placenta. Haematoxylin and eosin. (D) The subplacenta is fully developed and is situated below the main placenta and within the basal decidua. Haematoxylin and eosin. Am = amnion, bd = basal decidua, cd = capsular decidua, fvr = fibrovascular ring, int = interlobar areas, lab = labyrinth, mp = main placenta, pys = parietal yolk sac, sub = subplacenta, uc = uterine cavity, vys = visceral yolk sac. Scale bars = 1 cm (A), 1.5 mm (C-D).