Electron microscopy image of a cross section of the human placental barrier at term (IMAGE)
Caption
Vitamin D must be transferred from the maternal blood across the layers of the human placental barrier to the foetus, as shown in this electron microscopy image. The maternal blood fills the intervillous space and vitamin D crosses a continuous barrier called the syncytiotrophoblast (white arrows). Metabolism occurs within this layer and substances exit across the foetal-facing basal membrane and basal lamina (black arrows). The connective tissue of the stroma lies between the syncytiotrophoblast and the foetal capillaries.
Credit
Ashley et al. (CC BY 4.0)
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CC BY