Cavitation is a process in earlyembryonic development that followscleavage. Cavitation is the formation of theblastocoel, a fluid-filled cavity that defines theblastula, or in mammals theblastocyst.[1] Afterfertilization, cell division of thezygote occurs which results in the formation of a solid ball of cells (blastomeres) called themorula. Further division of cells increases their number in the morula, and the moruladifferentiates them into two groups. The internal cells become theinner cell mass, and the outer cells become thetrophoblast.[2] Before cell differentiation takes place there are twotranscription factors,Oct-4 andnanog that are uniformly expressed on all of the cells, but both of these transcription factors are turned off in the trophoblast once it has formed.[2]
The trophoblast cells formtight junctions between them making the structure leakproof. Trophoblast cells havesodium pumps on their membranes, and pump sodium into the centre of the morula. This draws fluid in through osmosis causing a cavity to form inside the morula, and to increase in size.[2] The cavity is the blastocoel. Following the formation of the blastocoel, the inner cell mass positions itself in one portion of the cavity, while the rest of the cavity is filled with fluid, and lined with trophoblasts.[1][3]
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