Figure Legend
Diagram of a terminal villus of a human placenta showing the surface covered by microvilli at the base of which are clathrin-coated vesicles for receptor-mediated endocytosis and also macropinocytotic channels for fluid uptake, via which microparticles from the maternal blood in the intervillous space may also be ingested. Particulate matter would have to traverse the trophoblast and be discharged before penetrating both trophoblast and endothelial basal laminae plus the endothelium itself before entering the fetal circulation. Particles may also be taken up by mesenchymal cells rather than entering the fetal capillary. Precision is therefore crucial when characterising particle location in tissue, whether it be in the trophoblast, mesenchyme, or endothelium as well as its position within the villous tree or chorionic plate6.