Fig. Purkinje cell dendritic spines. On the left, a longitudinally sectioned spine with smooth endoplasmic reticulum (arrow) and a cluster of polyribosomes located at the origin of the spine from the dendrite (D). Adjacent and synapsing with the same bouton is another, transversally sectioned spine. On the right, a transversally sectioned dendritic spine with smooth endoplasmic reticulum in the head (large arrow). Nearby spine necks are embedded in a glial process (small arrow). Scale = 200 nm. (Rat, mouse, cerebellar cortex.) Download the high resolution image; Download the high resolution image(a).