浙江大学医学院：肾脏的排泄功能（尿液的浓缩与稀释）Urinary concentration and dilution

Urinary concentration and dilution Concentrative urine浓缩尿: Osmolality of urine> plasma osmolality (300mOsm/LH2O) Di| uted urine稀释尿: Osmolality of urine plasma osmolality

Urinary concentration and dilution Concentrative urine浓缩尿: Osmolality of urine > plasma osmolality (300mOsm/L H2O) Diluted urine稀释尿: Osmolality of urine < plasma osmolality

Formation of Diluted Urine Isosmotic reabsorption of water at proximal tubule Impermeable of water at thick ascending limb LADH> Reabsorption of water at distal tubule and collecting duct>Diluted urine

Formation of Diluted Urine • Isosmotic reabsorption of water at proximal tubule • Impermeable of water at thick ascending limb • ADH→ Reabsorption of water at distal tubule and collecting duct → Diluted urine

Formation of concentrative Urine 个ADH→↑ Reabsorption of water at dist tubule and collecting duct>Concentrative Urine ADH--key element of urinary concentration and dilution What is the drive force of water reabsorption at distal tubule and collecting duct

Formation of Concentrative Urine • ADH→  Reabsorption of water at distal tubule and collecting duct → Concentrative Urine • ADH---key element of urinary concentration and dilution What is the drive force of water reabsorption at distal tubule and collecting duct ?

The osmotic Gradient of the rena medulla THE MEDULLARY OSMOTIC GRADIENT: REVIEW Cortical collecting duct CORTEX PCT DCT Cortex 300 300 Medulla 40 400 1200 OF H MEDULLA onal section the kidney Medullary collecting duct

The Osmotic Gradient of the Renal Medulla

Formation of osmotic Gradient of the renal medulla N Interstitial fluid osmolality ephron (mOsm/kg H,O) Permeability of the 300 Tubular HzO NaCl 300 System NaCI H2O medulla H,O 600 H,O NaCH NaCl HO medulla 1200 NaCl HO H. red

Formation of Osmotic Gradient of the Renal Medulla Permeability of the Tubular System

Permeability of the Tubular System HO Nacl Urea Thin descending +十 limb Thick ascending Actively transport limb Thin ascending limb Distal tubule + ADH Actively transport Cortical + ADH Actively transport collecting duct Inner medullary + ADH Actively transport++ collecting duct

Permeability of the Tubular System H2O NaCl Urea Thin descending limb ++ _ _ Thick ascending limb _ Actively transport _ Thin ascending limb _ + + Distal tubule + ADH Actively transport _ Cortical collecting duct + ADH Actively transport _ Inner medullary collecting duct + ADH Actively transport ++

Formation of osmotic Gradient of the renal medulla ☆ The countercurrent theory 1. Countercurrent M multiplication逆流倍 增 与星

❖ The countercurrent theory ➢ 1. Countercurrent multiplication逆流倍 增 A B C Formation of Osmotic Gradient of the Renal Medulla Na+ H2O

1. Countercurrent multiplication Interstitial fluid osmolality NaCl H2O - NoCI 300 Nac M2 HO 60 H2 NoCI HO 1200 Nac H O H2O

1.Countercurrent multiplication Na+ H2O

Establishing of Osmotic Gradient of the Rena/Med∥l s Outer medulla (1 Proximal tubule 4 Distal tubule Nacl Nutrients H O reabsorption of Nacl at cOHO个K Nac HCO hick ascending limb→ hyperosmolality CORTEX 2 Descending tHick segment limb of of ascending e Inner medulla op of Henle NaCl HO 1)urea recycling OUTER Nacl MEDULLA 2)reabsorption of NaCl 3 Thin segment6Collecting of ascending at thin ascending Urea Nacl H2o limb-> hyperosmolality MEDULLA

Establishing of Osmotic Gradient of the Renal Medulla  Outer medulla: reabsorption of NaCl at thick ascending limb → hyperosmolality  Inner medulla: 1) urea recycling 2) reabsorption of NaCl at thin ascending limb→ hyperosmolality

Urea recvcling Urea Urea buchu inme dulla HO Increased osmolarity I.O medulla Urea Ureal H2O Favors nore Diffusion back water reabsorption into tubule T rea