Blastocyst

The blastocyst ( Greek: βλάστη emited "sprout ", "seed"; κύστις kystis "bubble" ) is ( marsupials and Higher mammals) that stage of development during embryogenesis, following the formation of the morula in most mammals. The development of the blastocyst is referred to as blastogenesis or Blastulation.

In the embryogenesis of humans to develop this morula from the intercellular fluid-filled intercellular spaces, which eventually flow together about three to four days after fertilization the blastocyst cavity, thus forming the eponymous bubble within the first compact cell structure. Filling the intercellular fluid is effected by differentiation of the inner and outer cells of the morula. While the inner cells via gap junctions are in communication, from the outer form cell tight junctions across a stable delineation outwardly flat. Furthermore, can only develop on the outer cell microvilli.

With this polarization of the cell, an active fluid flow is triggered inside the morula through the outer cells. As a result, forms the blastocyst, the volume in its interior rises and it emerges from the zona pellucida ( egg case ) from. This process is supported by an enzymatic decomposition of the zona pellucida. The inner cells of the morula - embryoblast or the inner cell mass ( ICM) - remain on one side only receive ( embryonic pole) while forming from the surrounding cells of the trophoblast - a protective shell, arising out of, finally, placenta and fetal membranes be.

From blastocysts, embryonic stem cells ( ES cells) can be obtained. Here, the blastocyst is destroyed. This type of stem cell derivation is ethically controversial.

• Blastogenesis
• Reproductive Medicine