Carnegie stage 1

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Facts: Week 1, size 0.1-0.15 mm

Features: zygote, fertilized oocyte, pronuclei, polar bodies, zona pellucida

This image shows an early human zygote where the male and female pronuclei (centre of image) have not yet combined to form the single zygote nucleus.

Two of the egg's polar bodies (right, 3 o'clock position of image) are shown at the edge of the egg cytoplasm. These polar bodies contain the excess DNA from the meiotic divisions of the egg.

The zona pellucida (edge of image) forms a specialised thick extracellular matrix layer around both the egg and the developing conceptus for the first week.

Additional Images

Stage1 size with ruler

Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline

Cite this page: Hill, M.A. (2024, April 23) Embryology Carnegie stage 1. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Carnegie_stage_1

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