Morula

A morula ( from Latin: morum = mulberry ), also referred to as " Morula ", is in biology a stage of development during early embryogenesis of multicellular organisms such as humans.

It is at the morula to a spherical cell clusters from 8 to 32 cells ( blastomeres ), stating after the first divisions of the zygote. In humans is referred to as the 16- cell stage to about four days after the fertilization of a morula. At this time, the cell clusters usually in the fallopian tubes. The volume of the morula is unchanged from the zygote, since both are surrounded by the rigid zona pellucida, a layer of glycoproteins. The diameter is 150 microns. The zona pellucida is to stabilize the shape of the early seedling stage, for the prevention of implantation in the fallopian tube and protection from immunological reactions of the mother until the 6th day ( blastocyst stage ) were obtained.

At the stage of the morula, the cells in an inner and an outer cell mass, which is not yet externally distinguish differentiate. This impermeable cell junctions the outer cells form among themselves ( tight junctions ) and so separate the inner cell mass from the outer liquid medium. With this step, the cells lose their totipotency and are pluripotent. This forms the basis for the formation of the blastocyst and trophoblast differentiation in the outside, emerge from the placenta and fetal membranes, and in the embryoblast within, out of which the actual embryo develops.

In artificial insemination, the embryos are typically used in an early morula stage.

From the morula to blastula or in non- egg-laying mammals, the blastocyst is.