Renal Corpuscle Development in the Dog

Renal vesicle formation and glomerular development were studied in the 44-day dog fetus with the use of the scanning electron microscope. In the early stages of glomerular development the luminal aspect of the columnar glomerular epithelium shows a cobblestone appearance with sparse microvilli and occasional cilia. Marginal club-shaped processes are the earliest sign of prodocyte process development. These interdigitate with neighboring cell processes and elongate before developing definitve foot processes. Glomerular epithelial differentiation is uneven and multifocal, but once started, proceeds rapidly. The capsular epithelium progresses from cuboidal (in the vesicular stages) to squamous (in the mature glomerulus) with the area adjacent to the proximal convoluted tubule being the last area to differentiate fully.