Growth cone

A growth cone is a dynamic, actin-supported extension of a developing neurite 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. He first described the growth cone based on fixed cells as “a concentration of protoplasm of conical form, endowed with amoeboid movements” (Cajal, 1890). Neuronal growth cones are situated on the very tips of nerve cells on structures called axons and dendrites. The sensory, motor, integrative, and adaptive functions of growing axons and dendrites are all contained within this specialized structure.

Structure

The morphology of the growth cone can be easily described by using the hand as an analogy. The fine extensions of the growth cone are known as "filopodia" or microspikes. The filopodia are like the "fingers" of the growth cone; they contain bundles of actin filaments (F-actin) that give them shape and support. Filopodia are the dominant structures in growth cones, and they appear as narrow cylindrical extensions which can extend several micrometres beyond the edge of the growth cone. The filopodia are bound by membrane which contains receptors and cell adhesion molecules that are important for axon growth and guidance.