Blastocyst formation begins about 5 days after fertilization, when a fluid-filled cavity opens up in the morula, a ball consisting of a few dozen cells. The blastocyst has a diameter of about 0.1-0.2 mm and comprises 200-300 cells following rapid cleavage 5-6 days post-fertilization
Blastocyst possesses an Inner cell mass (ICM) which subsequently forms the embryo. The outer layer of the blastocyst consists of cells collectively called the trophoblast. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoele. The trophoblast gives rise to the placenta.
The use of blastocysts in in-vitro fertilization (IVF) involves culturing a fertilized egg for five days before implanting it into the uterus. It can be a more viable method of fertility treatment than traditional IVF.
DAY 5 EMBRYO (BLASTOCYST STAGE) with Cavity and Inner cell mass in Embryology Lab