Antral follicle

[2] The antral follicle is marked by the formation of a fluid-filled cavity adjacent to the oocyte called the antrum.

Granulosa and theca cells continue to undergo mitosis concomitant with an increase in antrum volume.

By command of an oocyte-secreted morphogenic gradient, the antral follicle's granulosa cells begin to differentiate themselves into four distinct subtypes: corona radiata that surrounds the zona pellucida, membrana that is interior to the basal lamina, periantral that is adjacent to the antrum, and cumulus oophorus that connects the membrana and corona radiata granulosa cells together.

[3] However, it does not appear to add any predictive information about success rates of an already established pregnancy after IVF.

[5] Three-dimensional (3D) automated follicular tracking is a developing technique that can substantially decrease both intra- and inter-observer variability in estimating the AFC.