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Two pronuclei dismantling in the central cytoplasm

TEM of a late stage 1c embryo in vitro showing two pronuclei in the central cytoplasm with a interpronuclear area, 24 hours post-insemination (original magnification x6,630). Cytoplasmic organelles are abundant around the pronuclei particularly dense mitochondria (M). The lower paternal pronucleus shows a protuberance (arrowhead). The envelope of the maternal pronucleus above is beginning to dismantle. This occurs just before syngamy. Both pronuclei have dense, compact nucleoli and a few intrapronuclear annulate lamellae (IAL).

GC = Golgi complex
S = vesicular smooth endoplasmic reticulum

From: Sathananthan, 1984. Reproduced with permission of the publisher, Churchill Livingstone.

Keywords: Golgi complex, cytoplasm, cytoplasmic organelles, maternal pronucleus, mitochondria, nucleolus, paternal pronucleus, pronucleus, stage 1c embryo, syngamy, vesicular smooth endoplasmic reticulum

Source: The Virtual Human Embryo.