Fig. 1.4.1.06. This dendritic spine (S) contains a cistern of smooth endoplasmic reticulum in its head (arrow), directed to a punctum adherens attaching an astrocyte process (a). The similar cistern (arrow) comes to the punctum from the astrocyte side. AT - axon terminal. Scale = 200 nm. (Human, neocortex.) Download the high resolution image.