Fig. 1.5.04. Axon terminal emerging from the myelinated portion (M) and forming a presynaptic bouton (B). Preterminal myelin loops filled with the oligodendroglial cytoplasm are apparent and dense septations are formed between the loops and axonal plasma membranes (blue arrow). P - the perikaryon of a pyramidal cell, red arrow - coated endocytotic vesicle in a dendritic spine. Scale = 400 nm. (Mouse, neocortex.) Download the high resolution image.