Zur Morphologie des Corpus ciliare und seiner Anhangsgebilde im Licht- und Rasterelektronenmikroskop bei verschiedenen Vogelarten

Georg, Christine Elisabeth Structure of the ciliary body and its annexes in different bird species: a light- and scanning electron microscopic study. The aim of this study was to clarify the structure of the ciliary body and its annexes in different bird species. Therefore the ciliary body, the chamber angle, the fibrae zonulares and the iris of 52 birds of 19 different species were examined systemically for the first time, not only by light microscopy, but also by scanning electron microscopy. Vicarious for the different types of bulbi oculi were examined gallinaceous birds, day-active and night-active predatory birds. The examination showed that the general anatomy of the ciliary body is equal in all birds. It can be divided morphologically into two parts from posterior to anterior: the posterior part of the pars plicata and the anterior part of the pars plicata. A prelenticular pars plicata, pars plana and transitional region of the iris, as it exists in mammals for the production of the aqueous humour, cannot be found in birds. In the avian eye, the aqueous humour is produced by the anterior part of the pars plicata. Large species-specific differences in the content of elastic fibres in the ciliary body could be found. Gallinaceous birds, day-active predatory birds and the cormorant use lenticular accommodation. Their ciliary body therefore contains many elastic fibres, while in night-active predatory birds, which almost exclusively use corneal accommodation, the ciliary body contains almost none. The size of the different portions of the ciliary muscle depend on the kind of accommodation used in the various bird species. In gallinaceous birds and day-active predatory birds, both main parts of the ciliary muscle, the ciliaris anterior and posterior muscle are equal in size. In contrast to this, the anterior portion in night-active predatory birds and the posterior portion in the cormorant is much larger. The avian-specific active accommodation requires an extremely deep cilioscleral sinus in all bird species. The width of the chamber angle depends on the bulbus type. In gallinaceous birds it is narrow, while in night-active predatory birds it is wide open. In day-active predatory birds its width is intermediate. The pectinate ligament in the bird is not strong enough to support the structure of the ciliary body. It consists of thin, mostly parallel cords which pull the ciliary body back into a relaxed postion when the ciliaris posterior muscle relaxes. In contrast to this, in the cormorant eye, the pectinate ligament consists of a very dense network of thick fibres. The examination of the Schlemm's canal showed clearly, that birds have a sinus venosus sclerae, in contrast to the plexus venosus sclerae in most mammals. In the anterior part of the iris of the examined Phasianus colchicus, Tinnunculus tinnunculus, Hierofalco rusticolus and Haliaeetus leucocephalus epitheloid cells were found, which are similar to the pigment cells, typical to many night active predatory birds.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Ludwig-Maximilians-Universität

Year

2003

Author dc:creator

• Georg, Christine

Repository record source_url

https://edoc.ub.uni-muenchen.de/990/

OAI identifier oai:identifier

oai:edoc.ub.uni-muenchen.de:990