Comparative Anatomy of the Trigeminal Nerve : Motor and Primary Sensory Neurons

The trigeminal nerve of vertebrates innervates the sensory and motor structures in the most rostral part of the body. Its morphological features vary both in the peripheral nervous system and in the central nervous system according to the animal behaviors it mediates. Some species possess very specialized sensory receptors innervated by the trigeminal nerve. Such are the barbels of hag fishes (cyclostomes) , the infrared receptive pits of certain snakes (reptiles) , the bills of ducks (birds) , and the vibrissae of rodents (mammals). These specialized sansory receptors of necessity require a specialized and very complex sensory processing system (the special sensory nuclei in the central nervous system) and the accompanying specialized motor systems in both the central and peripheral nervous systems. Although it is difficult to compare these very complex trigeminal systems from a phylogenetical standpoint , the sensory processing and masticatory mechanisms clearly become more sophisticated as one progresses from the primitive vertebrates up the phylogenetical tree. I have attempted here to illustrate the evolution of the vertebrates by presenting some morphological features of the trigeminal nervous system in the peripheral and central nervous systems in various members of this phylum.

三叉神経

体性感覚

顎運動

脊椎動物

比較解剖学