What are the three zones that form in the neural tube during spinal cord development?

By the fifth week, the neural tube develops three concentric zones: the Matrix (Ependymal) Zone (produces neuroblasts and spongioblasts), the Mantle Zone (forms gray matter), and the Marginal Zone (forms white matter).

How does the sulcus limitans divide the neural tube in spinal cord development?

The sulcus limitans divides the lateral wall of the neural tube into two laminae: the Alar Lamina (dorsal, sensory/afferent) and the Basal Lamina (ventral, motor/efferent).

What are the functional columns derived from the alar and basal laminae in the spinal cord?

The alar lamina forms two afferent columns: General Somatic Afferent (cutaneous and proprioceptive input) and General Visceral Afferent (visceral input). The basal lamina forms two efferent columns: General Somatic Efferent (innervates skeletal muscles) and General Visceral Efferent (preganglionic autonomic fibers).

How does the position of the spinal cord change from development to adulthood?

Initially equal in length to the vertebral column, the spinal cord ascends due to faster vertebral growth. It ends at S1 by week 24, L3 at birth, and the lower border of L1 (conus medullaris) in adults.

What structures form below the conus medullaris in the adult spinal cord?

Below the conus medullaris, descending nerve roots form the cauda equina, which surrounds the filum terminale (a fibrous extension of the pia mater).

What is the modern theory regarding the initial layers of the neural tube?

The modern theory states that all layers initially consist of pluripotent neuroepithelial cells forming a pseudostratified epithelium, with the zonal appearance reflecting stages of interkinetic nuclear migration during mitosis.

Spinal Cord Development – Grey Horns & White Tracts