Changes

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All cells in the embryo up to this stage are totipotent and divide asynchronously. After the 8-celled stage, a ball of cells is formed and is referred to as a '''morula'''. A '''morula''' has '''tight junctions''' formed between outer cells and '''gap junctions''' between the inner cells enabling them to polarise as a group and effectively create two distinct groups of cells within the morula. The outer cells pump sodium into the intracellular spaces and water follows osmotically allowing fluid  to begin to accumulate within the morula.

* These cells are totipotent and divide asynchronously.

* After the 8-celled stage, a ball of cells is formed.  This stage is referred to as a '''morula'''.

* '''Tight junctions''' form between outer cells of the morula.

Cells within the '''morula''' continue to divide and a '''blastocyst''' (see above) develops, consisting of an '''inner cell mass''' or (ICM), a '''blastocoele''' cavity and a single layer of '''trophoblast''' cells. As fluid accumulates, the outer cells become flattened and a cavity known as the blastocoele is formed. At this stage, two separate cellular components emerge - the '''inner cell mass''' and the '''trophoblast'''.

* '''Gap junctions''' form between inner cells of the morula.

* Thus, two groups of cells are created within the morula.

* Outer cells pump sodium into the intracellular spaces and water follows osmotically.

* Fluid begins to accumulate within the morula.

 

 

* Cells of the morula continue to divide and a '''blastocyst''' develops, consisting of:

** '''Inner cell mass''' (ICM)

** '''Blastocoele''' cavity

** Single layer of '''trophoblast''' cells

* As fluid accumulates, the outer cells become flattened and a cavity known as the blastocoele is formed.

* As a result, two separate cellular components emerge - the inner cell mass and the trophoblasts.