Morphology And Fiber Connection Of Cells In Layers A-H Of Chick Optic Tectum

Brids, as a good material for the research of the animals'visual system, have excellent visual capacity. Poultry is one of vertebrate which is the most dependent on the visual system. Approximately 90% of the retinal ganglion cells contribute to the tectofugal pathway in chick. The optic tectum is very important to visual system. In order to furtherly understand the structure of avian optic tectum in mesencephalon, the morphological characteristics and fiber connection of tectal cells in layer A-H of chick optic tectum were investigated using DiI (1,1'- dioctadecyl- 3,3,3'3'- tetramethylindo- carbocyanine perchlorate) retrogradely labeling method. The results showed that in the were studied by DiI retrogradely labeling. Various kinds of cell forms exist in the optic tectum. The soma of A-H cells showed various shape. Most of those cells appeared to be shuttle, round, oval, pyramidal, triangular, and polygonal etc. had large dendritic fields of unknown shape. Observation on C cells showed that the average long diameter, average short diameter and average area were 17.76±1.92μm, 12.43±2.30μm and 173.57±42.47μm~2 (n=45); Observation on D cells showed that the average long diameter, average short diameter and average area were 18.91±2.23μm, 13.05±2.31μm and 185.58±42.15μm~2 (n=45); Observation on E cells showed that the average long diameter, average short diameter and average area were 15.20±0.93μm, 13.74±1.30μm and 162.17±18.95μm~2 (n=45); Observation on F cells showed that the average long diameter, average short diameter and average area were 22.02±5.71μm, 13.54±1.94μm and 218.33±42.73μm~2 (n=45); Observation on G cells showed that the average long diameter, average short diameter and average area were 19.83±1.57μm, 17.51±1.81μm and 277.76±56.46μm~2 (n=45); Observation on H cells showed that the average long diameter, average short diameter and average area were 21.04±3.40μm, 14.92±3.37μm and 250.27±79.64μm~2 (n=45). The two different types of neurons,"typeⅠcell s"and"typeⅡcell s"were identified Based on the amount of the primary dendrites in layer A-D and layer F-H of optic tectum, Some of the"typeⅠcell s"gave out 2-3 primary dendrites, and some of the"typeⅡcell s"gave out 4-6 primary dendrites. Most of the cells in layers C-H of optic tectum project to the layers B,C and F. In the layer of F, some dendrites of the H cell come into synaptic relation with the dendrites of A-F cell. The optic fibers penetrate to various levels of the underlying stratum and there are wide and complicated fiber links in and between the layers of optic tectum.