Fig. 1

Partial structure of oocyte cumulus complex (OCC). A Light microscope image of a follicle with a diameter of about 135 μm (left). A schematic diagram (right) illustrates the follicle structure. B 2D SEM image of a part of OCC. C Reconstructed 3D model of the same part of the OCC. D-F Three consecutive SEM image sections focusing on the same granulosa cell with the transzonal projections (TZP) structure. G-H Reconstructed SEM image of Fig. 1d highlighting the granulosa cell, TZP and zona pellucida. I Reconstructed 3D model of a cGC with TZP. The red rectangular box represents the TZP structure