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Drawing of the head of a four-week-old human embryo. From Gray's Anatomy. Embryo drawing is the illustration of embryos in their developmental sequence. In plants and animals, an embryo develops from a zygote, the single cell that results when an egg and sperm fuse during fertilization. In animals, the zygote divides repeatedly to form a ball ...
The cells of the inner cell mass (embryoblast), which are known as human embryonic stem cells (hESCs), will further differentiate to form four structures: the amnion, the yolk sac, the allantois, and the embryo itself. Human embryonic stem cells are pluripotent, that is, they can differentiate into any of the cell types present in the adult ...
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Mesoderm embryonic tissues (paraxial mesoderm, intermediate mesoderm, lateral plate mesoderm and notochord). Also showing the neural tube and the yolk sac . Paraxial mesoderm
In all vertebrates, these progenitor cells differentiate into all adult tissues and organs. [5] In the human embryo, after about three days, the zygote forms a solid mass of cells by mitotic division, called a morula. This then changes to a blastocyst, consisting of an outer layer called a trophoblast, and an inner cell mass called the embryoblast.
Other cells migrate through the caudal part of the primitive line and form the lateral mesoderm, and those cells migrating by the most caudal part contribute to the extraembryonic mesoderm. [11] [15] The embryonic disc begins flat and round, but eventually elongates to have a wider cephalic part and narrow-shaped caudal end. [10]
The first cell division of a zygote is asymmetric, resulting in an embryo with one small cell (the apical cell) and one large cell (the basal cell). [22] The small, apical cell will eventually give rise to most of the structures of the mature plant, such as the stem, leaves, and roots. [ 23 ]
The bilaminar embryonic disc, bilaminar blastoderm or embryonic disc is the distinct two-layered structure of cells formed in an embryo.In the development of the human embryo this takes place by day eight.