Embryo Development and Neurulation

Overview

• By day 16, the embryo consists of three primary layers:
  • Endoderm
  • Mesoderm
  • Ectoderm
• The ectoderm develops into the nervous system.

Neurulation Process

Day 18: Neural Plate Formation

• Neuralation: The process of the neural plate becoming the neural tube.
• Neural Plate: Part of the ectoderm thickens, forming the neural plate.
• Location: Between cranial end and primitive node.

Day 19: Neural Groove and Folds

• Neural Groove: The neural plate begins to buckle in the midline, creating the neural groove.
• Neural Folds: Mounds on either side of the neural groove.

Day 21: Neural Tube Formation

• Fusion: Neural folds progress towards each other and begin to fuse.
• Neural Tube: The fusion forms a hollow cylinder known as the neural tube.

Cranial and Caudal Neuropores

• Neuropores: Unfused portions are called cranial and caudal neuropores.
  • Cranial Neuropore: Closes around day 24.
  • Caudal Neuropore: Closes around day 26.

Neural Crest Cells

• Located at the peaks of the neural folds.
• Form a layer over the closed neural tube.
• Develop into most of the peripheral nervous system.

Summary

• Neurulation results in the formation of the neural tube from the neural plate.
• Closure of neural folds begins in the center and zips towards both ends.
• Central Nervous System: Developed from the neural tube.

Additional Information

• By this stage, the embryo starts curving into the fetal position.
• Visual representations show the embryo at 21 and 31 days.
• Neural Tube: Curves through the back of the embryo.

Conclusion

• The schematic animation illustrates the neurulation process, simplifying the ectoderm as flat for clarity.

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