The cellular history of the glomerulus

Knowledge about the structure and functions of the cells of the glomeruli has accumulated slowly over the past 350 years. Marcello Malpighi originated the work, but it failed to progress far until Schleiden and Schwann developed their cellular theory in 1839. William Bowman linked the glomeruli to the tubules, described the parietal epithelial cells, the basement membranes, and (with Robert Todd) apparently first identified endothelial cells. Electron microscopy contributed especially to an understanding of epithelial and endothelial cell structure. Axel Key first described mesangial cells, but acceptance of these fell into abeyance for many years until Yamada incontrovertibly demonstrated their existence. Techniques such as tissue culture and molecular biological investigations have, more recently, provided much information about glomerular cell function. Progress has, throughout, depended upon the discovery of ever more powerful methods of microscopy, the development of ancillary experimental methods, the formulation of persuasive explanations for observations, and the suggestion of succinct terminology to describe the features observed.