Afferent arteriole
Efferent arteriole
Glomerulus
Filtration & arteriolar tone → sets GFR
Proximal tubule
Bulk Na⁺/water, glucose, HCO₃⁻ reabsorption; osmotic gradient
Thick ascending limb
NKCC2 — water-impermeable, builds medullary gradient, lumen-positive voltage
Distal convoluted tubule
NCC — fine Na⁺ and Ca²⁺ tuning
Collecting duct
ENaC, MR pathway, V2 / AQP2 water channels
↓ urine