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Reproductive Science - Clinical Embryology images of human preimplantation embryos - 2PN
After a sperm enters an oocyte, the male and female chromatin form two distinct pronuclei (PN).These appear as two round structures in the middle of the oocyte (now termed a zygote). They are aligned next to one another, but remain as two distinct orgnalles. The chromosomes are yet to mix. The alignment is termed "abuttal".
Within each PN are nucleolar precursor bodies (NPBs), seen in the images as little circles close to the abuttal. NPBs may also be called nucleoli. NPBs are attached to chromatin. If the chromatin is correctly aligned within the PN, the NPBs will appear polarised and "line up" as at the abuttal. Zygotes can be assessed for quality at this stage, and a "Z-score" allocated according to the level of NPB alignment,
During IVF treatment, clinical embryologists check from the presence of PN around 16-18 hours after the sperm has been added to the oocyte.
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| Contributed by: | Pathology Portal |
| Authored by: |
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| Licence: | © All rights reserved More information on licences |
| Last updated: | 12 July 2023 |
| First contributed: | 15 April 2023 |
| Audience access level: | Full user |
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