The extraglomerular mesangial cells are continuous with and resemble normal mesangial cells. They are linked to the granular cells via gap junctions, and they share a basement membrane and interstitium with the adjacent macula densa cells. Thus the extraglomerular mesangium appears to serve as the signaling intermediary between the tubular and vascular components of the juxtaglomerular apparatus.

The granular cells are similar to ordinary smooth muscle cells but have sparser smooth muscle myosin and contain numerous renin-filled vesicles. Because they produce large quantities of hormones, these cells also feature a prominent endoplasmic reticulum and Golgi apparatus.

Finally, the macula densa cells appear distinct from the neighboring tubular cells; a detailed description is available on Plate 1-25.