I meant circulatory peristaltic system, valves making bleeding out almost impossibility and thickness would be caused by big number of erythrocytes and there would not be central point but web like medieval country; there is lot of cities and route using road A could be rerouted if road A would be destroyed. And moving uncounscious body is like carrying it around.

@pojo-guy I think that evolved version of the organ allowing for breaching exoskeleton would work for skull if packed with harder "teeth" and stronger muscles.