During cell division, the number of stem cells increases, but the number of different cell types produced are limited. After 5 days of division hollow ball of blastocyst cells are formed.
The outer blastocyst cell layer forms the placenta that provides nourishment to the fetus.
Pluripotent embryonic stem cells ( ES cells) are formed from the inner group of stem cells and help in formation of the embryo's tissues.
Pluripotent cells are more versatile than an adult stem cell and can produce many different cell types.
These cells are easier for controlling growth and differentiation than adult stem cells.
Pluripotent stem cells are more abundant than adult stem cells and therefore significantly easier to isolate.
Research studies done on animal ES cell (Pluripotent embryonic stem cells) experiments can be used to understand Human stem cells.
Human pluripotent stem cells can be produced from:
Isolation of ES cells from blastocyst during in vitro fertilization.
ES cells can be extracted from eggs or sperms of aborted or miscarried fetus.
Production of tailor made ES cells from patients own differentiated cells by using cloning techniques.