Diabetic glomerulosclerosis.

I would like to show first the glomerulus of a 92-year-old man who did not have diabetes. It is perfectly normal. I want to emphasize that in the glomerulus there is not necessarily any ageing phenomenon per se. With the electron microscope there may be a slight increase in the thickness of the basement membrane of the glomerular capillary, but it is not visible by light microscopy. In the normal glomerulus the afferent arteriole breaks up into capillary loops which spread out to form the lobules of the glomerulus. The central portion of each lobule or group of capillary loops is called the mesangial area (fig. 1). The capillary loops themselves are lined with endothelial cells, consisting of nuclei which protrude into the lumen, and a widely spread-out thin layer of fenestrated cytoplasm lining the capillary lumen. The endothelial cell is separated from the epithelial cell by a thin layer of basement membrane, and this basement membrane connects with little processes of similar material between adjoining mesangial cells. Outside the basement membrane are the epithelial cells, each with a wide extension of foot processes, forming a network around the capillary, with a tiny canaliculi between each foot process.