Comparative Morphology of Trigeminal Ganglion in Some Species of Vertebrates

Abstract

The reported examinations were carried out on turtles, Japanese quails and chinchillas of either sex. The trigeminal nerve was studied with the modified thiocholine method and routine histological techniques. The trigeminal ganglion of the turtle is a single, compact structure connected with the trigeminal nerve. Analysis of consecutive sections showed a presence of ganglionic neurocytes only at the medial side of the trigeminal nerve. A small number of nerve cells and large number of fibres is characteristic for the investigated structure.The trigeminal ganglion of Japanese quail is a structure connected with two branches (ophthalmic and mandibular) of the trigeminal nerve. Both parts of the ganglion distinctly differ in their morphology. The part connected with the ophthalmic branch – V1 forms a thickening of the nerve, which becomes narrow approaching the orbital cavity. The second part connected with the mandibular branch – V2 is of regular shape. This part of the ganglion is located in the vicinity of a delicate maxillary branch. Histological investigations allow us to observe a characteristic arrangement of neurocytes with only one layer of nerve cells on the surface of the ganglion. The trigeminal ganglion in chinchilla is a single, irregular cluster of neurocytes closely connected with trigeminal nerve where this nerve divides into ophthalmic and maxillary nerves. Agglomerations of neurocytes allow us to distinguish two parts of trigeminal ganglion. From the medial aspect, the nasal part of ganglion is connected with this part of the trigeminal nerve, which is not distinctly divided into ophthalmic and maxillary branches. The caudal part of the trigeminal ganglion is connected with the mandibular branch of trigeminal nerve. These two parts are separated from each other by the motor radix of the trigeminal nerve. From the lateral side all parts of the ganglion form one structure and it is difficult to distinguish precisely different cell aggregations corresponding to the particular branches of trigeminal nerve.