metaphase II
Pronunciation: MET-ah-faze too
Also written as: MII — metaphase II
The stage of meiotic division where mature oocytes arrest prior to fertilization, representing optimal timing for intracytoplasmic sperm injection.
Full Definition
Metaphase II (MII) is the second stage of meiotic division where mature oocytes naturally arrest until fertilization occurs. At this stage, the oocyte has completed its first meiotic division, extruded the first polar body, and is characterized by chromosomes aligned at the metaphase plate. This represents the optimal maturation stage for assisted reproductive procedures, particularly intracytoplasmic sperm injection, as the oocyte is capable of normal fertilization and embryonic development. In laboratory settings, MII oocytes are identified by the presence of the first polar body and clear cytoplasm, distinguishing them from immature germinal vesicle or metaphase I stage oocytes. The timing and proportion of MII oocytes retrieved is an important quality indicator in ART cycles.
Usage
Usage note: Commonly abbreviated as MII; distinguish from other meiotic stages.
In Context
- "Twelve oocytes were retrieved, with ten reaching metaphase II stage suitable for ICSI." — Laboratory embryology report
- "The metaphase II oocytes demonstrated normal morphology with visible polar bodies." — Oocyte assessment documentation