Organizing the Multicellular Embryo
How does the zygote acquire the complex shape of the adult organism? Gastrulation marks the onset of changes in cell behavior that begin to shape the organism. As a consequence of gastrulation, the embryo becomes a trilaminar entity, with an outer layer of ectoderm, an inner endoderm and an intermediate layer of mesoderm. Cells of these layers then assemble into the organ and tissue rudiments and, ultimately, the functional organs and tissues that characterize the adult.
Cells can undergo changes either autonomously or in conjunction with their neighbors to form the embryo. Obviously, the consequences of changes in cell shape and motility will be quite different if cells are joined in an epithelium than when they are unconstrained by neighbors. The major morphogenetic process that involve mesenchymal and epithelial cells during embryogenesis are summarized by Gilbert (1997), Fig. 3.1 and by Kalthoff (1996), Fig. 10.3.
We shall now examine the following mechanisms of morphogenesis in detail, based upon recent progress in the field.
Gilbert, S.F. 1997. Developmental Biology. Fifth edition. Sinauer. Sunderland, MA.
Kalthoff, K. 1996. Analysis of Biological Development. McGraw-Hill. New York.
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Leon Browder & Laurie Iten (Ed.) Dynamic Development
Last revised Thursday, June 25, 1998