Fig. 4. Schematic of a mature glomerulus in cross section. Fewer capillary loops are shown than normal for clarity, and the size of cells are exaggerated in proportion to the overall size of the glomerulus. The four major cell types of the glomerulus are the Bowman's capsule (BC) or parietal epithelium (gray), podocytes (P, blue) or visceral epithelium, mesangial cells (M, orange) and endothelial cells (E, red). The mature glomerulus is encompassed by the Bowman's capsule. The glomerulus comprises a self-contained network of capillary loops (C, red), with mesangial cells forming a nexus at the base of the capillary network. The glomerular basement membrane (GBM, green) divides the glomerulus into two compartments, an inner one containing the capillaries and the mesangial cells, and an outer one containing podocytes and the space into which the filtrate passes. The glomerulus remains connected to the remainder of the nephron through an opening in the Bowman's capsule that connects the glomerulus to the proximal tubule, shown on the right. The arrows in the capillaries indicate the flow of blood in and out of the glomerulus. Also omitted for clarity is the branching of the single capillary loop into the multiple loops within each glomerulus.