Unmegsured L055s.. 500 intake 1500 Urine100
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A counter current multiplier 300 300 300 300 200 300 200 300 300 200 1 300 300 300 2 300 400 200 3 400 400 200 4 300 300 200 300 300 300 300 400 200 400 400 200 400 400 400 300 300 300 300 400 200 400 200 400 400 400 300 150 300 150 300 300 100 -P ⑤ 300 350 150 6 350 150 Repeat Steps 4-6 700 700 500 400 500 300 00 300 1000 1000 800 400 500 300 500 300 1200 1200 1000
A counter current multiplier
Active transport of a Na*/2Cl-/K*complex in the ascending limb of the loop of Henle NaCI H2O Urea H2O NaCI 300 /300 100 300 Na*/2Cl-/K* 600 600 600 600 H201 NaCl H。od2 NaCl Urea- elInpaw 1200 1200 120 1200
Na+/2Cl-/K+ Active transport of a Na+/2Cl-/K+ complex in the ascending limb of the loop of Henle
Vasa recta Interstitium mOsm/L mOsm/L 300 350 300 Solute H2o- 600 Solute 600 600 600 Solute- H0- 800 Solute 800 800 Solute 900 H20-1000 Solute 1000 1000 1200 1200 Figure 28-6 Countercurrent exchange in the vasa recta.Plasma flowing down the descending limb of the vasa recta becomes more hyperos- motic because of diffusion of water out of the blood and diffusion of solutes from the renal interstitial fluid into the blood.In the ascending limb of the vasa recta,solutes diffuse back into the interstitial fluid and water diffuses back into the vasa recta.Large amounts of solutes would be lost from the renal medulla without the U shape of the vasa recta capillaries.(Numerical values are in milliosmoles per liter
100%remaining 4.5 Urea 4.5. Urea--. 100% remaining Cortex 50%remaining 30 30 Outer H2O《-- medulla 15 Urea Inner 300 300 medulla 500 550 Urea 20%remaining Figure 28-5 Recirculation of urea absorbed from the medullary collecting duct into the interstitial fluid.This urea diffuses into the thin loop of Henle,and then passes through the distal tubules,and finally passes back into the collecting duct.The recirculation of urea helps to trap urea in the renal medulla and contributes to the hyperosmolarity of the renal medulla.The heavy dark lines,from the thick ascending loop of Henle to the medullary collecting ducts,indicate that these segments are not very permeable to urea.(Numerical values are in milliosmoles per liter of urea during antidiuresis,when large amounts of antidiuretic hormone are present.Percentages of the filtered load of urea that remain in the tubules are indicated in the boxes
Recycling of NaCl and urea in the renal medulla ↓ A highly concentrated zone Water diffusion from the renal tubules to the urinary medulla
Recycling of NaCl and urea in the renal medulla A highly concentrated zone Water diffusion from the renal tubules to the urinary medulla
NaCl H,O NaCl 300 300 300 100 100 NaCl 400 70 400 NaCl 400 H20 NaCl 600 600 600 50 Figure 28-2 Formation of a dilute urine when antidiuretic hormone(ADH)levels are very low.Note that in the ascending loop of Henle,the tubular fluid becomes very dilute.In the distal tubules and collecting tubules,the tubular fluid is further diluted by the reabsorption of sodium chloride and the failure to reabsorb water when ADH levels are very low.The failure to reabsorb water and continued reabsorption of solutes lead to a large volume of dilute urine. (Numerical values are in milliosmoles per liter.)
NaCI H2O Urea H,O NaCl 300 300 100 300 NaCl 600 600 600 600 H20 H20 NaCl Urea 1200 1200 1200 1200 ↓ Figure 28-4 Formation of a concentrated urine when antidiuretic hormone (ADH)levels are high.Note that the fluid leaving the loop of Henle is dilute but becomes concentrated as water is absorbed from the distal tubules and collecting tubules.With high ADH levels,the osmolarity of the urine is about the same as the osmolarity of the renal medullary interstitial fluid in the papilla,which is about 1200 mOsm/L.(Numerical values are in milliosmoles per liter