One sheet of ectoderm folds inward and becomes the brain. A handful of cells peel off the edge and become almost everything else above the diaphragm. Get the split right and twenty clinical questions become one.
Watch a flat sheet of ectoderm become a folded tube. Tap the stages. The blue is what becomes the central nervous system. The pink is what wanders off to build everything else.
Once the tube closes (Day 28), the cranial end balloons into three bumps. By week 5 those three become five. Tap any node to light up its lineage path. Cyan tags mark which ventricle each piece holds.
Week 4: three vesicles. Week 5+: five vesicles. After that the names lock in and the adult brain is just inflation.
Everything central. Brain, cord, the bits that look peripheral but are technically CNS tracts (retina, optic nerve, posterior pituitary).
Rule of thumb: if it sits inside the skull or vertebral canal and is wrapped by dura, it is neural tube. The exception is the posterior pituitary, which is literally a downgrowth of the diencephalon hanging out of the floor of the brain.
Crest cells delaminate off the dorsal lip of the closing neural tube and migrate everywhere. They become almost every "neural-ish but not central" structure plus a few surprises (calcitonin-secreting C cells, the heart outflow septum, facial bones).
When a vignette gives you a derivative, ask one question first: is this in the central nervous system or has it gone walkabout? That answer chooses the column.
| Feature | Neural Tube | Neural Crest |
|---|---|---|
| Origin | Neural plate that folded inward · closed off from ectoderm | Cells at the tips of neural folds · delaminated as the tube closed |
| Stays put? | Yes · remains in the midline | No · migrates all over the body |
| Major derivatives | Brain, cord, retina, optic nerve, pineal, posterior pituitary, CNS glia (astrocytes, oligodendrocytes, ependymal) | PNS ganglia, Schwann cells, melanocytes, adrenal medulla, thyroid C cells, leptomeninges, facial bones, spiral septum of heart |
| Endocrine output | Posterior pituitary (ADH, oxytocin storage); pineal (melatonin) | Adrenal medulla (catecholamines); thyroid C cells (calcitonin); enterochromaffin (serotonin) |
| Myelin maker | Oligodendrocytes (CNS) | Schwann cells (PNS) |
| Failure pattern | Neural tube defects (spina bifida, anencephaly) · prevented by folate | Neurocristopathies: Hirschsprung, DiGeorge, Waardenburg, Treacher Collins, conotruncal heart defects |
| Classic tumors | Medulloblastoma, ependymoma, pinealoma, glioma | Schwannoma, melanoma, pheochromocytoma, neuroblastoma, medullary thyroid carcinoma |
| Mnemonic | "Inside the box" | "MOTEL PASS" wanderers |
The pituitary looks like one gland on imaging. It is actually two completely different tissues that met in the middle of the skull base. One came up from the roof of the mouth. One came down from the brain.
Most "neural crest vs neural tube" questions are clean. The exam writers earn their salary on these three. Internalize them before the test.
The lecture pattern is one axis: rostral closure, caudal closure, forebrain splitting, and posterior fossa shape. Tap a defect and force the location before the name.
The same anatomy in canonical illustrations. Tap to enlarge. These are the figures the clinical medicine and the textbooks are drawing from.
clinical questions with explanations that walk through every wrong answer. No time pressure. Read the wrong-answer chains: they are where the points come from.
