09/07/2025
A good Metaphase II (M2) oocyte : exhibits specific microscopic features indicative of its maturity and quality, including a spherical shape, a single, normal-sized first polar body (PB), a uniform zona pellucida (ZP), a pale cytoplasm with a homogenous and translucent texture free of inclusions, and an appropriate perivitelline space (PVS).
Key Microscopic Features of a Good M2 Oocyte:
Ooplasm:
The cytoplasm should be uniform, translucent, and homogeneous in texture, appearing pale and lacking visible inclusions, vacuoles, or organelle clustering.
First Polar Body (PB):
A single, well-formed polar body of appropriate size should be present, located between the ooplasm and the zona pellucida.
Zona Pellucida (ZP):
The ZP should be uniform in thickness and appearance, appearing continuous and smooth around the oocyte.
Perivitelline Space (PVS):
A small and appropriate perivitelline space, the area between the oocyte and the zona pellucida, is also a sign of a good quality oocyte.
Shape and Size:
The oocyte should have a regular, spherical shape and a size within the normal range for human oocytes.
Absence of Granularity or Inclusions:
While cytoplasm can be granular due to organelles, excessive granularity, vacuoles, or other inclusions are considered signs of compromised quality.
Image Details :
Different human oocyte morphological abnormalities (arrows) observed by light microscopy (400× magnification): (A) diffuse cytoplasmic granularity, (B) centrally located cytoplasmic granular area, (C) smooth endoplasmic reticulum clusters, (D) vacuoles, (E) abnormal zona pellucida shape, (F) large perivitelline space with fragments
