MICROANATOMY

Detailed explanation-1: -The organism in a stage between zygote to fetus is called an embryo* and the cells are called embryonic stem cells. At this point embryonic stem cells have the ability to become a cell for any part of the body (nerve, muscle, blood, etc.). This ability to become any type of cell in the body is called pluripotent.

Detailed explanation-2: -As the zygote divides, the cells it differentiates into form the many different cell types of the fetus and eventually the adult: skin, muscle, nerve, hair, bone, etc. The process of differentiation proceeds in a stepwise fashion and involves changes in gene expression.

Detailed explanation-3: -Stem cells divide to form one daughter cell that remains a stem cell and a second that differentiates (e.g., to an intestinal epithelial cell). A good example of the continual proliferation of stem cells is provided by blood cell differentiation.

Detailed explanation-4: -Embryonic stem (ES) cells are fully pluripotent in that they can differentiate into all cell types, including gametes.