RenalProcesses_SpecificNarrated

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Renal processes Specific: Renal Clearance and GFR Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings.

III. Basic Renal Exchange Processes:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. III. Basic Renal Exchange Processes Glomerular filtration Reabsorption Secretion

Basic Renal Processes:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Basic Renal Processes Glomerular filtration—from glomerulus to Bowman’s capsule Reabsorption—from tubules to peritubular capillaries Secretion—from peritubular capillaries to tubules Excretion—from tubules out of body

Renal Exchange Processes:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.7 Renal Exchange Processes

Filtration:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Filtration Bulk flow of plasma Glomerular capillaries to renal capsule Movement of protein-free plasma from glomerulus to Bowman’s capsule GFR = 125 mL /min or 180 liters/day

Renal Corpuscle:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.8 (1 of 3) Renal Corpuscle

Renal Corpuscle:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.8 (2 of 3) Renal Corpuscle

Starling Forces Favoring Filtration Across Glomerulus:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Starling Forces Favoring Filtration Across Glomerulus Glomerular capillary hydrostatic pressure 60 mm Hg High due to resistance of efferent arteriole Bowman’s capsule oncotic pressure 0 mm Hg Low due to lack of protein in filtrate

Starling Forces Opposing Filtration Across the Glomerulus:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Starling Forces Opposing Filtration Across the Glomerulus Bowman’s capsule hydrostatic pressure 15 mm Hg Relatively high (compared to systemic capillaries) due to large volume of filtrate in closed space Glomerular oncotic pressure 29 mm Hg Higher than in systemic capillaries due to plasma proteins in smaller volume of plasma

Glomerular Filtration Pressure:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.9a Glomerular Filtration Pressure

Regulation of GFR:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Regulation of GFR 180 liters fluid filtered/day Only 1.5 liters urine excreted/day (<1%) >99% of filtered fluid is reabsorbed Small increase in GFR  large increase volume fluid filtered and excreted GFR highly regulated

Regulation of GFR:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Regulation of GFR Intrinsic mechanism Myogenic regulation Smooth muscle in wall of afferent arteriole Contracts in response to stretch Tubuloglomerular feedback Macula densa cells secrete paracrine in response to an increase in flow of fluid past them Smooth muscle of arteriole contract in response to this paracrine

Effect of MAP on GFR:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.10 Effect of MAP on GFR

GFR: Myogenic Regulation:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.11a GFR: Myogenic Regulation

GFR: Tubuloglomerular Regulation:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.11b GFR: Tubuloglomerular Regulation

Extrinsic Control of GFR:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Extrinsic Control of GFR Decreases in BP can decrease GFR Directly (decrease in filtration pressure) Indirectly through extrinsic controls

Reabsorption:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Reabsorption Selective transport; renal tubules to interstitial fluid Movement from tubules into peritubular capillaries (returned to blood) Most occurs in proximal tubule Most is not regulated

Normal Rates of Filtration and Reabsorption:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Table 18.1 Normal Rates of Filtration and Reabsorption Most of these substances are reabsorbed!

Solute Reabsorption:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Solute Reabsorption Most occurs in proximal convoluted tubule Some in distal convoluted tubule Barrier for reabsorption Epithelial cells of renal tubules Endothelial cells of capillary (minimal)

Reabsorption Barrier:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.13 Reabsorption Barrier

Active Solute Reabsorption:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.14a Active Solute Reabsorption

Water Reabsorption:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.14b Water Reabsorption

Passive Solute Reabsorption:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.14c Passive Solute Reabsorption

Transport Maximum:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Transport Maximum Rate of transport when carriers are saturated When solute transported across epithelium by carrier protein, saturation of carriers can occur

Renal Threshold:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Renal Threshold For a solute which is normally 100% reabsorbed If solute in filtrate saturates carriers, then some solute excreted in urine Solute in plasma that causes solute in filtrate to saturate carriers and spillover into urine = renal threshold

Example: Glucose Reabsorption:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Example: Glucose Reabsorption Freely filtered at glomerulus Normally 100% actively reabsorbed in proximal tubule Normally, no glucose appears in urine

Glucose Reabsorption:

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 18.15 Glucose Reabsorption Carrier proteins for glucose reabsorption Apical membrane: secondary active transport Basolateral membrane: facilitated diffusion

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