1. Placental Morphology Features
Placental shape (diffuse, cotyledonary, zonary, discoidal)
Definitive type of placental interface (eg. epitheliochorial, endotheliochorial, hemochorial)
Fetomaternal interdigitation (folded, villous, labyrinthe)
Fetomaternal blood flow interrelations (concurrent, countercurrent, crosscurrent, multivillous)
Placental nutrient transport
Wildman D, et al., 2006

2. Placental structure is highly diverse among mammals
Thornburg and Faber, 1983

3. hu ^
Thornburg and Faber, 1983

4. Placental Morphology Features
Placental shape (diffuse, cotyledonary, zonary, discoidal)
Definitive type of placental interface (e.g. epitheliochorial, endotheliochorial, hemochorial)
Fetomaternal interdigitation (folded, villous, labyrinthe)
Fetomaternal blood flow interrelations (concurrent, countercurrent, crosscurrent, multivillous)
Placental nutrient transport
Wildman D, et al., 2006

5. The functions of the placenta are to establish a dialogue with maternal physiology for the success of pregnancy, and to provide nutrients for fetal growth and development.
Many variations on the interface can be found and terminologies have evolved as morphological tools became more sensitive.
Stroma

6. Fetal and maternal blood are separated by 1 capillary and (a) fetal epithelium: Hemochorial placentation (trophoblasts are directly exposed to maternal blood; human, rat, mouse, monkey).
Kaufmann and Burton, 1994
Moffett and Lake, 2006

7. Placental Morphology Features
Placental shape (diffuse, cotyledonary, zonary, discoidal)
Definitive type of placental interface (e.g. epitheliochorial, endotheliochorial, hemochorial)
Fetomaternal interdigitation (folded, villous, labyrinthe)
Fetomaternal blood flow interrelations (concurrent, countercurrent, crosscurrent, multivillous)
Placental nutrient transport
Wildman D, et al., 2006

8. Villous Week 1 of gestation: Trophoblast differentiation
Syncytio-trophoblast differentiation
Invasion and formation of the trophoblastic shell
No villous organization
Villous
Benirschke and Kaufmann, 1999

9. Extravillous trophoblast differentiation
Week 2 of gestation:
Extravillous trophoblast differentiation
Syncytio-trophoblast expansion
Formation of fetal vasculature
Initiation of villous organization
Benirschke and Kaufmann, 1999

10. Villous placentation

11. Placentation in primates: spiral artery remodeling
Rapid invasion of spiral arteries: endovascular invasion
Limited interstitial trophoblast invasion
Remodeling of vessel wall
Invasion to endometrial-myometrial junction around 1/3 of gestation
Enders, 2007
CTK IHC

12. Inappropriate remodelling may lead to hypoxic, nitrative or oxidative stress and is thought to have clinical significance in adverse pregnancy outcomes.
Genbacev et. al,
2001

13. Placental Morphology Features
Placental shape (diffuse, cotyledonary, zonary, discoidal)
Definitive type of placental interface (e.g. epitheliochorial, endotheliochorial, hemochorial)
Fetomaternal interdigitation (folded, villous, labyrinthe)
Fetomaternal blood flow interrelations (concurrent, countercurrent, crosscurrent, multivillous)
Placental nutrient transport
Wildman D, et al., 2006

14. Chorionic
plate
Villus
tree
Basal plate
Decidua
Ramsey and Harris, 1966

15. Adamson et al, 2002 This shows mouse placenta, but the idea of
placental layers in the same for humans and
other primates

16. Placental Morphology Features
Placental shape (diffuse, cotyledonary, zonary, discoidal)
Definitive type of placental interface (e.g. epitheliochorial, endotheliochorial, hemochorial)
Fetomaternal interdigitation (folded, villous, labyrinthe)
Fetomaternal blood flow interrelations (concurrent, countercurrent, crosscurrent, multivillous)
Placental nutrient transport
Wildman D, et al., 2006

17. Blue, red, yellow: type I, II, III stem villi.
Pale blue, violet: terminal villi. These villi are thought to be the primary sites of nutrient transit to the fetal vessels.
Fuchs and Ellinger, 2004

18. During pregnancy, there is thinning of the syncytial layer and formation of close association between the basal syncytium and outer layer of the villous endothelium. This is thought to be a major transport zone.
Fuchs and Ellinger, 2004

19. Oxygen, glucose, amino acids, vitamins, ions, minerals, lipids, water
Fuchs and Ellinger, 2004
Needed nutrients:
Oxygen, glucose, amino acids, vitamins, ions, minerals, lipids, water
Potential mechanisms of transit: diffusion, carrier-mediated transport, vesicular transcytosis