Neural development

Neural development is a complex process in early embryogenesis responsible for the formation of the central nervous system (CNS), which includes the brain and spinal cord. This process begins with the formation of neural structures from the ectoderm layer of the embryo.

Key Stages in Neural Development

Day 18

Notochord Formation:
- The notochord forms from mesodermal cells and acts as a central structural support.
- It induces the overlying ectoderm to begin differentiation into neuroectoderm, leading to the formation of the neural plate.

Day 21

Neural Plate Formation:
- The neural plate forms as ectodermal cells respond to signals from the notochord.
- The plate eventually gives rise to critical neural structures: the neural tube and neural crest cells.

Structures in Neural Development

Neural Plate

Definition: A thickened region of ectoderm that eventually differentiates to form neural tissue.
Role: Gives rise to the neural tube and neural crest cells, forming the basis of the CNS.

Neural Fold

Definition: Raised edges of the neural plate that move towards each other.
Role: Fuse to form the neural tube, the precursor to the CNS.

Neural Crest Cells

Definition: Specialized cells at the edge of the neural plate that separate as the neural tube forms.
Role: Migrate throughout the embryo to form diverse cell types, including peripheral nervous system (PNS) components, melanocytes, and some craniofacial structures.

Neural Tube

Definition: A hollow structure formed from the fusion of the neural folds.
Role: Develops into the brain and spinal cord.

Notochord

Definition: A rod-like structure derived from the mesoderm.
Role: Induces the overlying ectoderm to form the neural plate.
Adult Derivative: Becomes the nucleus pulposus of intervertebral discs.

Alar Plate and Basal Plate in the Neural Tube

Plate	Location	Function	Regulation
Alar Plate	Dorsal	Sensory processing	TGF-β and BMP
Basal Plate	Ventral	Motor function	Sonic Hedgehog (Shh)

Alar Plate and Basal Plate in the Neural Tube

Orientation: The dorsal-ventral orientation of the alar and basal plates mirrors the organization of the adult spinal cord.

Points to Remember

The notochord is crucial for neural induction, prompting the ectoderm to form the neural plate.
Neural crest cells contribute to many structures outside the CNS, especially in the peripheral nervous system.
Alar and basal plates define sensory and motor regions in the developing spinal cord, regulated by specific signaling molecules (e.g., BMP for alar plate, Shh for basal plate).

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USMLE Step 1 Review Series

Curriculum

Neural development

Key Stages in Neural Development

Day 18

Day 21

Structures in Neural Development

Neural Plate

Neural Fold

Neural Crest Cells

Neural Tube

Notochord

Alar Plate and Basal Plate in the Neural Tube

Points to Remember

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