What is the function of the endoneurium, epineurium, fascicle, and perineurium?

A nerve consists of many structures including axons, glycocalyx, endoneurial fluid, endoneurium, perineurium, and epineurium. The axons are bundled together into groups called fascicles, and eachfascicle is wrapped in a layer of connective tissue called the perineurium.