Early morphogenesis of the canine lens capsule, tunica vasculosa lentis posterior, and anterior vitreous body. A transmission electron microscopic study.

This study provides transmission electron microscopic observations on the early morphogenesis (from days 25-35 post coitum) of the canine posterior lens capsule, the tunica vasculosa lentis (TVL) posterior and the anterior part of the vitreous body. The presence of an anlage of the posterior lens capsule as early as day 25, recently described histologically, was confirmed by this study. In the period from day 25 to day 35, the polar part of the posterior lens capsule develops 2-29 continuous and parallel lamellae, matching 50 nm and 1.74 microns, respectively. At these early stages, the TVL consists of capillaries that are simple endothelial tubes. From day 28 onward, these can be classified as A-1-alpha capillaries according to the classification of Bennett et al. [3]. In direct proximity to the lens capsule, the vitreous body contains fibrillar material with a morphological appearance similar to that of the lens capsule. This material probably derives from both the capillary endothelial cells' basal lamina and the lens capsule. Only few cellular components were observed in the anterior vitreous body. The development of the described structures is grossly in accordance with that observed in other mammalian species. The observations presented serve as a reference for studies on the pathogenesis of persistent hyperplastic tunica vasculosa lentis/persistent hyperplastic primary vitreous (PHTVL/PHPV), which is an important cause of leucocoria in children and in some dog breeds.