This video provides a detailed histological examination of the human spinal cord, emphasizing its basic structure and cellular components. The analysis differentiates between the central, neuron-rich gray matter (divided functionally into dorsal sensory and ventral motor aspects) and the peripheral, fiber-rich white matter (composed of ascending and descending tracts). Key cellular features are highlighted under high magnification, including large multipolar neurons (distinguished by the distribution of Nissl substance in axons vs. dendrites) and surrounding glial cells (astrocytes, oligodendrocytes, and microglia). The video also focuses specifically on the Central Canal, which is uniquely lined by ependymal cells, noting their simple columnar epithelial structure and role in lining the ventricular system of the CNS. The role of oligodendrocytes as the myelination cells within the CNS, contrasting with Schwann cells in the PNS roots, is also stressed.
Spinal Cord Histology: Gray Matter, White Matter, and Glial Cells
0:04 Spinal Cord Overview: The spinal cord is presented as a simple and beautiful structure for dissection and study, regardless of the level cut.
0:25 Gray vs. White Matter: The central butterfly-shaped area is gray matter (rich in neurons); the peripheral area is white matter (absent in neurons, composed of tracts).
0:40 Functional Segregation: The dorsal/posterior gray matter is devoted to sensory functions, while the ventral/anterior gray matter is devoted to motor functions, containing motor neurons.
1:06 White Matter Composition: White matter consists chiefly of ascending and descending myelinated tracts (axons) running to and from the brain.
1:20 The Central Canal: The central portion contains the Central Canal, which is lined by ependymal cells. Ependymal cells are a type of glial cell that also lines the ventricles and choroid plexus of the brain.
2:08 Review of CNS Tissues: Key components seen include large neurons, small glial cells, vascular spaces, and meningeal tissue (Arachnoid mater externally). The nerve roots surrounding the cord are PNS structures, consisting of Schwann cells surrounding axons.
3:11 Neuron and Glial Cell Identification: Under higher power, the large cells are confirmed as neurons and the surrounding smaller cells are glial cells.
3:46 CNS Myelination: Myelination within the central nervous system (CNS) is performed by oligodendrocytes, contrasting with Schwann cells in the peripheral nervous system (PNS).
4:00 Multipolar Neurons Detail: Multi-polar neurons are clearly visible. A key histological distinction is that Nissl substance (rough ER) extends into dendrites but stops abruptly where the axon begins.
5:09 Rules of Thumb: Neurons are approximately 10 times larger than astrocytes but are about 1/10th as common. The nucleus of a neuron is roughly the size of a whole nucleus of a glial cell.
5:30 White Matter Transition: The shift from fiber-rich gray matter to white matter is abrupt, showing cells (oligodendrocytes) surrounded by white, washed-out myelin.
6:31 Ependymal Cells Detailed View: The Ependymal cells lining the Central Canal are visualized clearly, noted for their unique appearance as a simple columnar epithelium among glial cells.