| spiral artery wall, Nichbaur layer, cytotrophoblast and Hofbaur layer |
| syncitiotrophoblast, cytotrophoblast, villi connective tissue and fetal capillary endothelium |
| maternal lacuna, trophoblast layer, endothelial and fetal red blood cell |
| fetal capillary endothelium, villi connective tissue, cytotrophoblast and syncitiotrophoblast |