Axon histology - what do we know about the length and shape?
Back in 1860, the German anatomist Otto Friedrich Karl Deiters was the first one to describe the basic structure of the nerve cell. A publication by Maria Rosaria Muzio gives a detailed overview on main axon histology and function properties. So what do we know about the axons as of today? It is an elongated portion of the neuron located in the center of the cell and filling nearly 95% of the total volume of the neuron. It serves to carry an electrical impulses to non-neuronal targets such as muscle fibers. Interestingly, the length of axons is based on the function of the neuron. Therefore, dendrites are limited to a small region around the cell body while axons reach longer distances. For example, the longest axons of the human body are in the sciatic nerve, reaching approximately one meter. Shape of the axons was always considered as cylindrical, however new 3D electron microscopy technology allowed to demonstrate that axon may not be a perfect cylinder. The diameter, same as length, is variable (1-25 micrometers) and depend on functional properties to allow a certain impulse speed. Stay tuned to find out about axon classification in coming reviews!