Fig. 3.

Photomicrographs of a wild-type placenta (A) and a P0 knockout placenta (B) selected to illustrate thin and thick examples of the exchange barrier (between maternal blood space and fetal capillary). Also illustrated are grids used in stereological analysis. (A) Cycloid arcs and a line grid have been superimposed as used for the estimation of surface densities and harmonic mean thickness respectively. (B) A grid of test points has been superimposed as used for the estimation of volume fractions. MBS, maternal blood space; FC, fetal capillary; T, trophoblast. (Bar = 10 μm.)