Kidney nontumor
General
Glomeruli

Author: Nikhil Sangle, M.D. (see Authors page)

Revised: 8 September 2017, last major update March 2012

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Kidney glomeruli [title]

Cite this page: Sangle, N. Glomeruli. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/kidneyglomeruli.html. Accessed November 22nd, 2017.
Definition / general
  • Tuft-like vascular structure composed of lobules of specialized capillaries that arise from an afferent arteriole and eventually coalesce to drain into an efferent arteriole
  • 200 microns in diameter, 20% larger in juxtamedullary area
Structure
  • Layers (inner to outer) are: fenestrated endothelium, then glomerular basement membrane (lamina rare interna, lamina densa and lamina rare externa), then podocytes (visceral epithelium with foot processes); also parietal epithelium which lines Bowman space (which contains the ultrafiltrate of plasma)
  • Glomerular basement membrane (GBM): normally 250 - 380 nm, composed of type IV collagen, laminin, polyanionic proteoglycans (mostly heparan sulfate), fibronectin and entactin
  • Type IV collagen forms suprastructure to which other glycoproteins attach; composed of 3 alpha chains
  • Each alpha chain has amino 7S domain, middle triple helical domain and a carboxyl noncollagenous (NC1) domain; NC1 domain is site of anti-GBM nephritis and dimer formation
  • Mesangial cells: type of myofibroblast that supports glomerular tuft, regulates capillary width and blood flow; are phagocytic and can proliferate; the mesangium on the capillary side is covered by endothelial cell; the capillary basement membrane extends to form the paramesangial basement membrane; at ultrastructural level, the mesangium shows cell membrane dense bodies (attachment plaques), which anchors the mesangial cell to the cell membrane
  • Podocytes (visceral epithelium): their foot processes embed in lamina rare externa of glomerular basement membrane; the distal diffusion barrier to filtration of proteins is a filtration slit diaphragm between foot processes
Glomerular filtration
  • Glomeruli are highly permeable to water and solutes through fenestrated endothelium; they are impermeable to large proteins like albumin (proteins are more permeable if smaller and more cationic)
Diagrams / tables

Images hosted on other servers:

Normal glomerulus

Vessels surrounding glomeruli and tubules

Microscopic (histologic) description
  • Hypercellularity: the presence of more than 3 cells in an individual glomerular mesangial region away from the vascular pole
Microscopic (histologic) images

Images hosted on other servers:

Various images of normal glomeruli



A: light microscopy; B: fluorescence microscopy with Hollande fixative distinguishes
proximal (heavy star) and distal (asterisk) convoluted tubules;
fluorescence microscopy shows thin and delicate glomerular loops,
smooth mesangial matrices

Special stains
  • PAS stain allows assessment of glomerular basement membranes, mesangial matrix and tubular basement membranes
  • Jones methenamine silver (JMS) highlights these better than PAS
  • Masson trichrome stain highlights hyalinosis, scarring, immune deposits and fibrinoid deposits