External granular layer (cerebral cortex)

External granular layer (cerebral cortex)

The external granular layer is a layer of the cerebral cortex. It is also known as layer II. It is one of the six layers of the cerebral cortex, and it is located just below the molecular layer (layer I).

Etymology

The term "external granular layer" is derived from its location and appearance. It is called "external" because it is located towards the surface of the cortex, and "granular" because it contains small, densely packed cells that appear granular in histological sections.

Structure

The external granular layer is composed of small pyramidal cells and numerous stellate cells. These cells are smaller and more densely packed than those in the other layers of the cortex. The pyramidal cells in this layer are smaller than those in the external pyramidal layer (layer III), and the stellate cells are similar to those in the internal granular layer (layer IV).

Function

The function of the external granular layer is not fully understood. However, it is believed to play a role in processing information from the thalamus and other parts of the brain. The stellate cells in this layer are thought to receive inputs from the thalamus and send outputs to other cortical layers.

Clinical significance

Abnormalities in the external granular layer have been associated with several neurological disorders, including schizophrenia and autism. However, the exact role of this layer in these disorders is not yet clear.

See also

• Cerebral cortex
• Cortical layers
• Molecular layer
• External pyramidal layer
• Internal granular layer

References

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