[The structure of bovine choriocapillaris]

The ultrastructure of bovine choriocapillaris was investigated in bovine choroid and isolated choriocapillary samples. The choriocapillaris lies in the layer just outside the Bruch's membrane. The choriocapillary endothelial cells on the side facing Bruch's membrane were found tapering their cytoplasm, with a significant number of fenestrae. The fenestrae were predominantly located in the choriocapillaris at the posterior pole, rather than at the periphery, of the eyeball. The endothelial cells on the side facing the sclera had few fenestrae, and the nuclei of endothelial cells and pericytes were located on this side. It was found that on the peripheral part of the choroid, the basement membranes of either choriocapillary endothelial cells or those of pericytes take part in composing the outer part of the Bruch's membrane. The isolated choriocapillaris revealed a typical lobular pattern of capillaries arranged in a radiating fashion. Intercellular junctions and/or cell contacts among endothelial cells and pericytes were also investigated.