Reabsorption and Secretion Along the Nephron Summary Table - Anatomy & Physiology

()Map REABSORPTION AND SECRETION ALONG THE NEPHRON (Map)

Substance	Proximal Tubule	Loop of Henle	Distal Tubule and Collecting Duct	Hormonal Influences
Sodium	Passively enters the cell via ion channels or co-transporters in the apical membrane. Is pumped out of the cell via the sodium/potassium ATPase in the basolateral membrane Link to Article	Passively reabsorbed via diffusion from the thin ascending limb Reabsorbed actively in the thick ascending limb via the Sodium/Potassium/2-Chloride co-transporter It is then cleared from the cell via the sodium/potassium ATPase in the basolateral membrane Link to Article
Potassium	Potassium mainly moves across the membrane via the paracellular route. It is then pumped into the cell in exchange for sodium via the sodium/potassium ATPase in the basolateral membrane It then leaves the cell using a co-transporter with chlorine Link to Article	Reabsorbed actively in the thick ascending limb via the Sodium/Potassium/2-Chloride co-transporter It also enters the cell via the sodium/potassium ATPase in the basolateral membrane Potassium from both these sources leaves the cell via a co-transporter with chlorine Link to Article
Urea	Is passively reabsorbed Link to Article
Water
Glucose	It is reabsorbed using a co-transporter with sodium via secondary active transport Link to Article	N/A	N/A	N/A
Protein	Is reabsorbed via endocytosis Link to Article	N/A	N/A	N/A
Calcium	Bulk reabsorption but not regulation of calcium occurs in the proximal tubule Link to Article	Calcium can passively move paracellulary into the vasa recta Link to Article
H+ and HCO3-	The secretion of H+ in this section of the nephron is mainly a result of the Na+/H+ antiporter in the apical membrane using secondary active transport. HCO3- is reabsorbed here in a different way to other substances. The presence of hydrogen in the lumen causes some amount of it to dissociate to carbon dioxide and water via the enzyme carbonic anhydrase. These enter the epitehlial cells where they are reformed using the same enzyme. The HCO3- then leaves the cell using the basolateral 3HCO3-/Na+ co-transporter. Link to Article
Organic Acids and Bases	Secreted here via primary active secretion. Link to Article	N/A	N/A	N/A