Placental Barrier

 Placental Barrier/ Placental membrane

Placental membrane is 0.25mm thick.

Placental membrane is partition between fetal and maternal circulation.

Where mother and fetus exchange gases, nutrients.

Membrane forms by; Syncytiotrophoblast, Cytotrophoblast, Embryonic connective tissue (Wharton's jelly), endothelium of fetal blood vessels.

Placental membrane separates maternal blood from fetal blood.

Fetal part of placenta is chorion.

Maternal component of placenta decidua basalis.

Oxygen and nutrients in maternal blood in intervillous spaces diffuse through walls of villi and enter fetal capillarie.

Carbon dioxide and waste product diffuse blood in the fetal capillaries through the walls of villi to maternal blood in intervillous space.

Thin alpha zones of terminal villi are for gas exchange.

Thick beta zones of terminal villi  (patches) are for hormone synthesis.

Increase in thickness of villus membrane seen in cases with IUGR and cigarette smokers.