胚胎发展lopment - Labster Theory - hth华体会最新网站

This is the process in which an organism develops from a single-celled zygote to a multicellular organism.

胚胎发展lopment is complex and well-regulated. Embryo development in humans is divided into following stages:

Fertilization
Cleavage stage
Blastula stage
Gastrulation
Organogenesis
Vertebrate formation

Nine weeks after fertilization, the human embryo is considered a fetus. There is no clear feature that distinguishes an embryo from a fetus. The term fetus implies that the embryo can be recognized as a human.

The embryo is pinkish against a red background. The embryo has a slightly rounded portion at one end, with an elongated tail like section curving in to form a C shape. Two small protrusions can be seen on the side, where limbs will later form.

7 weeks old human embryofrom Anatomy & Physiology, Connexions Web site.