Fine structure of the retinal epithelium, Bruch's membrane (Complexus basalis) and choriocapillaris in the domestic ferret.

The fine structure of the retinal epithelium, choriocapillaris, and Bruch's membrane has been studied by electron microscopy in the domestic ferret. The ferret possesses a tapetum cellulosum in the superior fundus, and the morphology of the retinal epithelium and its associated structures varies depending upon its relation to the tapetum. Over the tapetum the retinal epithelium is a single layer of low cuboidal cells with basal infoldings and two types of apical process. Internally the cells are non-pigmented, display much smooth endoplasmic reticulum, little rough endoplasmic reticulum, lysosomes, phagosomes, and a basally located nucleus. The choriocapillaris is composed of large capillaries indented into the retinal epithelium. Bruch's membrane is thin and composed of three layers. In non-tapetal regions the retinal epithelial cells are pigmented but display most of the other features noted over the tapetum. The choriocapillaris is not indented in non-tapetal areas. Bruch's membrane appears identical to that noted over the tapetum. Wandering phagocytes are occasionally noted at the retinal epithelium-photoreceptor junction.