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High-Yield Embryology Notes
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1. Neurulation (Weeks 3-4)
- Process: Notochord induces Ectoderm -> Neuroectoderm -> Neural Plate -> Neural Tube.
- Closure: Zips middle to ends. (Anterior: D25, Posterior: D27).
- Defects (NTDs): Low Folate (B9). High AFP/Acetylcholinesterase.
2. Brain Vesicles & Derivatives
"Tell Dad Me Met My Spouse" (Tel, Di, Mes, Met, Myel)
| Primary | Secondary | Adult Structures | Ventricle |
|---|---|---|---|
| Prosencephalon | Telencephalon | Cerebral hemispheres, Basal ganglia | Lateral |
| Diencephalon | Thalamus, Hypothalamus, Retina | 3rd | |
| Mesencephalon | Mesencephalon | Midbrain | Aqueduct |
| Rhombencephalon | Metencephalon | Pons, Cerebellum | Upper 4th |
| Myelencephalon | Medulla | Lower 4th |
3. Malformations
- Holoprosencephaly: Failed hemisphere separation. SHH mutation. Trisomy 13.
- Chiari I: Tonsils only. Syringomyelia.
- Chiari II: Tonsils + Vermis. Myelomeningocele.
- Dandy-Walker: Agenesis of Vermis. Huge 4th ventricle cyst.