chapter19b The Kidneys 2

chapter19b The Kidneys 2 - Chapter 19b The Kidneys...

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Chapter 19b The Kidneys
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Reabsorption Principles governing the tubular reabsorption of solutes and water Figure 19-11 Na+ is reabsorbed by active transport. Electrochemical gradient drives anion reabsorption. Water moves by osmosis, following solute reabsorption. Concentrations of other solutes increase as fluid volume in lumen decreases. Permeable solutes are reabsorbed by diffusion. Na+ Anions H2O K+, Ca2+, urea Tubular epithelium Extracellular fluid Tubule lumen Filtrate is similar to interstitial fluid. 1 2 3 4 1 2 3 4
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Reabsorption Transepithelial transport Substances cross both apical (lumen side) and basolateral membrane Paracellular pathway Substances pass through the junction between two adjacent cells
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Reabsorption Figure 19-12 [Na+] high [Na+] high [Na+] low K+ Na+ ATP Proximal tubule cell Interstitial fluid Tubule lumen Na+ reabsorbed Na+ enters cell through membrane proteins, moving down its electrochemical gradient. Na+ is pumped out the basolateral side of cell by the Na+-K+-ATPase. ATP = Active transporter = Membrane protein KEY Na+ Filtrate is similar to interstitial fluid. 1 2 1 2 Sodium reabsorption in the proximal tubule
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Reabsorption Sodium-linked glucose reabsorption in the proximal tubule Figure 19-13 = SGLT secondary active transporter = GLUT facilitated diffusion carrier [Na+] high [glu] low Na+ Na+ [Na+] high [glu] low glu glu [Na+] low [glu] high K+ ATP Glucose and Na+ reabsorbed + Na+ moving down its electrochemical gradient using the SGLT protein pulls glucose into the cell against its concentration gradient. Glucose diffuses out the basolateral side of
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chapter19b The Kidneys 2 - Chapter 19b The Kidneys...

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