An early human zygote due to the presence of male and female pronuclei in the centre of the cytoplasm. (see also labelled image)
The haploid pronuclei of the male (spermatozoa) and female (oocyte) have not yet combined to form a single nucleus.
The polar bodies can be seen at the edge of the cytoplasm (at 3 o'clock position). These exclusion bodies contain the additional oocyte DNA produced in meiosis.
The zona pellucida forms the thick clear layer that surrounds the cell.
At this stage in vivo:
- there would still be granulosa cells and spermatozoa attached to the zone pellucida.
- the zygote floats freely within the uterine tube.
- The cell is preparing for the first mitotic division.
About Carnegie Stages 1
Facts: Week 1, size 0.1 - 0.15 mm (100 - 150 microns)
Features: zygote, fertilized oocyte, pronuclei, polar bodies, zona pellucida
Image Source: UNSW Embryology http://embryology.med.unsw.edu.au/wwwhuman/Stages/Stage1.htm
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|current||11:45, 10 March 2012||500 × 441 (23 KB)||Z8600021|
|16:40, 27 July 2009||216 × 191 (4 KB)||MarkHill||About Carnegie Stages 1 Facts: Week 1, size 0.1-0.15 mm Features: zygote, fertilized oocyte, pronuclei, polar bodies, zona pellucida Image Source: UNSW Embryology http://embryology.med.unsw.edu.au/wwwhuman/Stages/Stage1.htm|
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