A<unk>  is a dynamic, actin-supported extension of a developing axon seeking its synaptic target. Their existence was originally proposed by Spanish histologist Santiago Ramón y Cajal based upon stationary images he observed under the microscope. Neuronal<unk> s are situated on the very tips of nerve cells on structures called axons and dendrites. The most crucial roles of the neuronal<unk>  are to explore its surroundings ultimately establishing synaptic contacts.
Growth cone
Articular processes
Optic stalk
Ganglion
Atlas 
Nucleohyaloplasm
Ependyma
Danger space