Medical Research Council - London Institute of Medical Sciences

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Sac in Time
25 September 2017

Sac in Time

Every pregnant woman knows that her waters breaking are a definite sign a baby is coming. Up until then a bag of nourishing chemicals, known as the amniotic sac, surrounds the new life. The sac bursts just before labour, but how it first develops is a little mysterious. Grown in a dish from human pluripotent stem cells, this 'embryoid' mimics cellular changes that happen when an embryo first implants in the womb. Cells (with their nuclei stained blue) organise themselves into a hollow ball shape called a cyst. The red-coloured cells are using a tell-tale embryonic gene called Oct4 – similar cells in the womb contribute to the embryo itself. At the top of the cyst (with its inner surface stained green) cells form a tough skin of amnion, defining the shape of the amniotic sac and producing a model that scientists can use to study development and fertility.

Written by John Ankers

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BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

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