Some of the apical dendrites from the pyramidal cells in the cerebral cortex may be up to 10μm in diameter. The apical dendrite of a large pyramidal neuron in the cerebral cortex may contain thousands of spines. Spines in the cerebral cortex vary in size by several orders of magnitude from one region to another. Smallest have a length of 0.2μm and a volume of about 0.04 cubic micrometres and the largest a length of 6.5μm and a volume of 2 cubic micrometres.