Embryonic stem cells refer to pluripotent cells that are generally derived from the inner cell mass of blastocysts (day 5).
Stem cells have been derived from gonadal ridges and mesenteries (3200 to 4000) extracted from aborted five-to-nine week old human embryos.
5-7 days embryonic cells are totipotent 6 week embryo cells are pluripotent
weeks 2-4
After a few weeks of conception, stem cells begin to differentiate into the organs of the developing embryo, with the formation of the heart being one of the earliest events. Around the third week of gestation, the heart starts to develop from mesodermal stem cells, marking a crucial step in organogenesis. This process sets the foundation for the development of other organs and systems in the body as the embryo continues to grow.
From the time a fertilized egg is implanted in a mother's uterus until about the eighth week of pregnancy, the developing organism is called an embryo.
The term "fetus" refers to the stage of development after the embryo. The two-cell stage of development comes well before the embryonic stage. There is no point at which a fetus, by definition, has two cells.
5-7 days embryonic cells are totipotent 6 week embryo cells are pluripotent
Embryo, between the 3rd and 8th week. Fetus, after the 8th week
weeks 2-4
In the first week an embryo is only a few cells large....barely able to be seen under a microscope.
The babies (embryo) heart starts to beat at about 4 weeks.
Week four
The stage of human development between zygote and fetus is the embryo stage. This stage typically lasts from the 3rd week to the 8th week after fertilization. During this time, the cells continue to divide and differentiate into the various organs and tissues of the body.
The embryo lasts until about week 10 or 11 and then it is known as a fetus.
In humans, the prefetal product of conception from implantation through the eighth week of development.
4th week
The mother does. The embryo attaches to the uterine lining (called implantation) then secretes an enzyme to breakdown the cells of the lining as it burrows into the uterus. Maternal uterine cells then develop and surround the entire embryo, soon maternal blood vessels unite with the embryo to nourish it and remove waste products. This occurs about one week after fertilization and will provide nourishment throughout the first trimester until the embryo reaches the fetal stage at which time the placenta takes over through the umbilical cord.
During week one, the embryo is still at the stage of implantation and does not have a measurable length. By the end of week ten, the embryo has developed into a fetus and is typically around 1.2 to 1.6 inches (3 to 4 centimeters) long.