What is neurulation and when does it occur?

Neurulation is the process where the neural tube forms from the ectoderm. It begins around day 16 with the neural plate and involves fusion of neural folds, starting at the 4th somite (~day 20) and completing by day 28.

What are the key structures formed from neural crest cells?

Neural crest cells migrate to form multiple structures, including dorsal root ganglia, sensory ganglia of cranial nerves, autonomic ganglia, adrenal medulla, melanocytes, and Schwann cells.

What is the difference between anencephaly and rachischisis?

Anencephaly results from failure of anterior neuropore closure, leading to an absent skull vault and degenerated brain. Rachischisis is a severe spina bifida from posterior neuropore failure, causing exposed neural tissue in the lumbosacral region.

What are ectodermal placodes and what do they contribute to?

Ectodermal placodes are localized thickened areas of neuroepithelium in the surface ectoderm. They contribute to special sensory structures, such as the lens and inner ear.

When do the anterior and posterior neuropores close during neural tube development?

The anterior neuropore closes by day 25 (18–20 somite stage), and the posterior neuropore closes by day 28 (~25 somite stage). This closure is critical for proper brain and spinal cord formation.

What happens if the neural tube fails to close properly?

Failure of neural tube closure can lead to congenital anomalies like anencephaly (from anterior neuropore failure) or rachischisis (from posterior neuropore failure), resulting in exposed or degenerated neural tissue.

Neurulation – Neural Tube & Neural Crest