Why is the cerebral cortex described as grey matter rather than white matter?

• A. Because it is made chiefly of myelinated axons
• B. Because it is heavily vascularized
• C. Because it is made from cell bodies rather than myelinated axons
• D. Because it contains fewer neurons

Answer: (C)

Grey color comes from what the tissue is built from. Where neurons have their cell bodies, dendrites, and synapses, the tissue appears grey; white color comes from densely packed, myelinated axons whose lipid-rich myelin gives a white sheen. The cerebral cortex sits on top of the brain and is rich in neuronal cell bodies and their dendrites, with relatively little myelin, so it looks grey. Deep to it, the white matter consists mostly of myelinated axons that connect cortical areas with each other and with subcortical structures, which is why that region appears white. So the cortex is described as grey matter because it is made primarily of cell bodies rather than myelinated axons.