• Macular densa: sensing Na flow at DCT, secreting NO → Dilate AA (afferent arteriole)
• Mesangial cells: smooth muscle–like cells connected to GBM, constrict → lower GFR
• Ganular cell: secrete renin under the signal of MD

Substance exchange membrane:

• Podocyte ****→ prevent Albumin from entering the urine
• Endothelium
• GBM (Glomerular basement membrane)