What is a Blastocyst?

A blastocyst is an embryo that has reached the 5th day of development. At this time, its structure is made up of a multitude of cells that have already begun to form a specialization and, therefore, it is possible to distinguish several parts of a blastocyst:

The trofoectoderm

are the cells that come in contact with the endometrium and, subsequently, will originate the placenta.

The internal cell mass (ICM)

is inside the trofoectoderm and is the structure that will give rise to the fetus.

The blastocele

is the central cavity of the embryo that is filled with fluid.

The zona pellucida

is a protective layer that surrounds the blastocyst until hatching occurs and the blastocyst detaches from it in order to implant.