Secondary Neurulation
In secondary neurulation, the neural ectoderm and some cells from the endoderm form the medullary cord. The medullary cord condenses, separates and then forms cavities. These cavities then merge to form a single tube. Secondary Neurulation occurs in the posterior section of most animals but it is better expressed in birds. Tubes from both primary and secondary neurulation eventually connect.
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Famous quotes containing the word secondary:
“Readers are less and less seen as mere non-writers, the subhuman “other” or flawed derivative of the author; the lack of a pen is no longer a shameful mark of secondary status but a positively enabling space, just as within every writer can be seen to lurk, as a repressed but contaminating antithesis, a reader.”
—Terry Eagleton (b. 1943)