-describe the 3 steps of embryonic development (cleavage division, gastrulation, organogenesis)

Cleavage, in embryology, in the first few cell divisions of the zygote. Initially, the zygote separates into the longitudinal axis. The second division is also longitudinal but at 90 degrees on the first plane. The process produces a multicellular embryo. It is an assembling process that divides the seed into developmental regions. Zygote cytoplasm includes chemicals that control gene expression.

Gastrulation is characterized as an early embryonic phase in which the embryo is converted from a one-dimensional layer of epithelial cells to a multilayer, multidimensional structure called the gastrula.

Organogenesis is a process of embryonic development that occurs at the end of gastrulation and lasts until birth. During organogenesis, the three germ layers formed by gastrulation (ectoderm, endoderm, and mesoderm) form the internal organs.

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that is wrong, its not thymus.