What kind of cleavage do human embryos undergo?
The human embryo goes through the following major stages during the course of its development: The blastomere stage, which is a two-celled stage results from the first division. It is claled the first cleavage. The holoblastic stage, which is a continuation of the first stage. The cells, during this stage, continue to divide again until the activity results in the stage of 16 cells. The cells at this point are roughly equal in size and are undifferentiated. The trophoblastic stage develops from this point. In this stage the organism consists of an outer layer of small cells. This layer is called a trophoblast. The cells surround a cluster of a few relatively larger cells. This area of the embryo is known as the inner cell mass. It is from this inner cell mass that the body of the new individual is to develop. The blastocystic stage sets in during or after the fourth day. During this stage, fluid accumulates between the cells of the segmented ovum, which soon becomes a blostocyst, or ho