For the first time, researchers can explain how a heart is formed in an embryo. This was done by observing the embryonic hearts of mice and as a result, there is the very real possibility of having a better understanding of why congenital heart defects occur.

Researchers from the Francis Crick Institute have been able to identify the cells that make up the heart during the embryonic stage of pregnancy. According to Medical Xpress, the stage of development that this has been observed in is during gastrulation.

Gastrulation, according to Microbe Notes, happens during the third week of gestation. During this time, three germ layers are produced that will eventually become all of the important embryonic tissues.

The three layers are called the ectoderms, endoderm, and mesoderm and each layer handles specific cells, determining where they will develop in the layer.

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The cardiovascular system and all the cells that help to develop it occur in the mesoderm layer.

According to the study, which was published in PLoS Biology, researchers were not only able to identify the specific cells that develop the heart but were also able to observe them from the time they developed through the time that the cardiovascular system was formed.

Researchers were able to identify that each cell's gene has a set designated destination when it comes to building the structure of the heart. And when they form the heart, the left ventricle is formed first, followed by the right, completing the heart with the two atria, according to Detonic.

Knowing the order in which the cells form the heart, researchers were able to observe them via advanced imaging technology by looking at mouse embryos as they developed outside of the body, according to Medical Xpress.

The researchers hope that by knowing the order in which the cells form the heart, it will be possible to determine the precise moment in which the development goes astray, leading to congenital heart disease. And for those 40,000 newborns who are born with congenital heart defects yearly, according to the Centers for Disease Control, there may be hope that intervention can be made before the second trimester of pregnancy.

If it is the case that changes in the cells can be made at such an early age, then hopefully the number of babies afflicted yearly can be dramatically decreased. Because even though congenital heart defects affect 1 percent of babies yearly, per Stanford Children's Health, it is still the most common of all birth defects. As such, finding a way to lower those numbers is imperative to saving lives and decreasing the need for surgeries in very young babies.

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Source: Medical Xpress, PLoS Biology, Detonic, Microbe Notes, Centers for Disease Control, Stanford Children's Health