Mesangium

The mesangium is an inner layer of the glomerulus, within the basement membrane surrounding the glomerular capillaries. This term is often used interchangeably with mesangial cell, but in this context refers specifically to the intraglomerular mesangial cells. These cells are phagocytic and secrete the amorphous basement membrane-like material known as the mesangial matrix. They are typically separated from the lumen of the capillaries by endothelial cells.