File:Fetal membrane and placenta cartoon.jpg

Schematic view of the fetal membranes and the placenta.

(A) The schematic view demonstrates the arrangement of the mesometrially situated embryo, the chorioallantoic placenta, positioned at the antimesometrial side, and the other fetal membranes inside the uterus, representing an advanced stage of pregnancy.

(B) In initial pregnancy, the placenta contains mainly of trophospongium with the developing subplacenta confluent to the main placenta. Strings of extraplacental trophoblast and syncytial streamers can be followed from towards the maternal blood channels.

(C) In early pregnancy, a labyrinth is established and the subplacenta represents a distinct organ. (D) Near term, the placenta is highly villous with the labyrinth as the dominant area. The subplacenta has been reduced. Red numbers in white boxes refer to subsequent figures with more detailed documentation of specific regions. Ce = central excavation, lab = labyrinth, mbc = maternal blood channel, pys = parietal yolk sac, sp = subplacenta, sys = syncytial streamers, tsp = trophospongium, uc = umbilical cord, ut = uterine tissue, vys = visceral yolk sac.

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Chorioallantoic placentation in Galea spixii (Rodentia, Caviomorpha, Caviidae) Moacir F Oliveira, Andrea Mess, Carlos E Ambrósio, Carlos AG Dantas, Phelipe O Favaron, and Maria A Miglino Reprod Biol Endocrinol. 2008; 6: 39. Published online 2008 September 4. doi: 10.1186/1477-7827-6-39. PMCID: PMC2543018

Placentas of guinea pig-related rodents are appropriate animal models for human placentation because of their striking similarities to those of humans. To optimize the pool of potential models in this context, it is essential to identify the occurrence of characters in close relatives.

Reprod Biol Endocrinol. 2008; 6: 39. Published online 2008 September 4. doi: 10.1186/1477-7827-6-39.