Blastocyst & Hatching

So the title of this post kind of makes it sound like I’m a chicken, right?  Before I got in the world of embryology, I had no idea that human embryos actually hatch out of their shells too. 

First things first though, yesterday my (possible) morula should have expanded out to a blastocyst.  A blastocyst is essentially made up of 2 parts; the Trophoblast (aka the trophectoderm) that becomes the placenta,   and the Inner Cell Mass that becomes the fetus.  In the first picture below on the left the Inner Cell Mass  is on the left side.  The rest of the cells that make up the cobblestone appearance are the trophoblast.  The shell around the embryo (looks like a halo) is called the Zona Pellucida.   

So possibly today or tomorrow, our little blastocyst should hatch out of its shell (the zona pellucida).  It has also been wandering its way from the ovary, through the fallopian tube, and should be entering the uterus yesterday or today. 

The picture on the right shows the blastocyst completely busting out.  Notice the empty shell left on the bottom right of the picture. 

So, after the embryo has hatched, it will burrow in and attach to the uterine lining.   This is when hCG (the hormone that turns pregnancy tests positive) can start to build up .  During the first trimester, hCG should double every 48-72 hours.   It won’t be until late next week sometime where a pregnancy test could possibly register a positive. So…. now we wait. 


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