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Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002.

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Cover of Molecular Biology of the Cell

Molecular Biology of the Cell. 4th edition.

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Figure 21-69. The blastula.

Figure 21-69The blastula

In the outermost regions of the embryo, tight junctions between the blastomeres begin to create an epithelial sheet that isolates the interior of the embryo from the external medium. Na+ is pumped across this sheet into the spaces in the interior of the embryo, and water follows into these spaces because of the resulting osmotic pressure gradient. As a result, the intercellular crevices inside the embryo enlarge to form a single cavity, the blastocoel. In Xenopus the wall of the blastocoel is several cells thick, and only the outermost cells are tightly bound together as an epithelium.

From: Cell Movements and the Shaping of the Vertebrate Body

Copyright © 2002, Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter; Copyright © 1983, 1989, 1994, Bruce Alberts, Dennis Bray, Julian Lewis, Martin Raff, Keith Roberts, and James D. Watson .


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