Summary
The three-dimensional arrangement of the zonular fibers of Zinn and their ultrastructure was studied with the aid of scanning and transmission electron microscopy.
Most of the thicker zonular fibers are arranged in straight bundles between the ciliary body and the lens, while the thinner fibers form a complex three-dimensional network interconnecting all the zonular fibers. These do originate from the limiting membrane covering the ciliary body. The zonular fibers are subdivided close to lens and form a complicated network on the surface of the lens capsule, i. e. the zonular lamella. The latter consists of a dense network of fibers and is from a structural point of view closely related to the zonular fibers and not to the lens capsule.
The zonular fibers are continuous with those in the vitreous body close to the ciliary body but never in the lenticular two thirds of the zonular fibers or in the retrolental area.
The ground substance is possible to demonstrate in freeze-dried specimens by scanning electron microscopy. It appeared granular or amorphous and coated the zonular fibers. It does not form membranes or fill all available space in contrast to its properties in the vitreous body. The many structural similarities between the zonular fibers and the vitreous body indicate perhaps a common origin.
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Supported by grants from “Magnus Bergwalls Stiftelse” and the Swedish Medical Research Council (B70-12 X -2543-02, B71-12 X -2543-03).
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Hansson, HA. Scanning electron microscopy of the zonular fibers in the rat eye. Z. Zellforsch. 107, 199–209 (1970). https://doi.org/10.1007/BF00335225
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DOI: https://doi.org/10.1007/BF00335225