Differentiated blastocyst structures

The 4th week of pregnancy is important, as it is perhaps the moment when the woman discovers that she is really pregnant due to the absence of the menstrual period and the first symptoms.

This is when the embryo reaches the endometrium and implants in the blastocyst stage. Here it is possible to clearly differentiate two structures:

• Trophoectoderm that will give rise to the placenta.
• Internal cell mass or ICM that will form the baby.