| At blastula stage 8, cells forming the blastocoelic roof were cultured in isolation as explants. |
| The ICM will also give rise to yet another extraembryonic tissue, the primitive endoderm, which is first visible as a cuboidal layer of cells lining the blastocoelic cavity on the fourth day of development. |
| The blastocoelic cavity usually collapses during the early stages of implantation. |
| An early blastocyst, containing a small amount of blastocoelic fluid, is shown to the right. |
| Some collapsed immediately while others still had some blastocoelic fluid at the end of the incubation period before loading on to the carriers. |
| The primitive endoderm then develops at the blastocoelic surface of the ICM, and migrates out across the inner surface of the blastocoel. |
