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Closure of the cranial neuropore is bidirectional, and final closure occurs in the area of the future forebrain. Closure of the caudal neuropore is strictly craniocaudal and finishes at the level of the second sacral segment.

This is what Larsen's Embryology says. I understand that neurulation starts somewhere in the area of the first five somites and then proceeds in both directions - cranial and caudal. The caudal neuropore is closed on day 26 by neurulation in this direction.

But, the cranial neuropore is closed not only by this cranial wave of neurulation but also by another one incoming craniocaudally and the point where they both meet is of final closure. (hence bidirectional)

My doubts - pls correct if any of my interpretations are wrong. Where is this second craniocaudal wave originating? Where is the final point of meeting (I suspect linea terminalis or anterior commissure) ? Could anyone post a picture or a reference to understand this visually (both waves of neurulation)?

PS. I am not talking of primary and secondary neurulation. Which is different and concerns the caudal eminence.

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Where is this second craniocaudal wave originating?

It begins in the prosencephalic region adjacent to the chiasmatic plate.

Where is the final point of meeting (I suspect linea terminalis or anterior commissure) ?

Cranial linea terminalis represents the zone of closure of cranial neuropore.

Could anyone post a picture or a reference to understand this visually (both waves of neurulation)?

Neural tube closure


Sources:

1: https://www.ncbi.nlm.nih.gov/pubmed/11948562

2: https://goo.gl/RLmQcj

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  • $\begingroup$ Thanks! A picture is truly worth more than a thousand words! I was breaking my head for so long, only if this pic was put into the books! $\endgroup$ – Polisetty May 21 '17 at 19:40
  • $\begingroup$ Links for them can be found in gray's anatomy. $\endgroup$ – JM97 May 22 '17 at 14:08

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