Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun1

Kidney and urine formation

Renal structure & functionUrine formationUrinary concentration and dilution

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yRegulation of urine formation

1)General functions

Kidney and urine formation1.Renal structure & function

1)General functionsExcretionRegulation of the internal environment

Water balanceNa+,K+ balance

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Acid-base balanceProduction of renin, erythropoietin, etc.

Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun2

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2)Renal structure Cortical nephron: 80-90%

Kidney and urine formation1.Renal structure & function

NephronRenal corpuscle: filtrationRenal tubule: reabsorption, secretion

Cortical nephron: 80 90%Juxtamedullary nephron

Collecting ductJ x l m l t s

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Juxaglomerular apparatusJuxaglomerualr cell ReninMacula densa Receptor : Na+

Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun3

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun4

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun5

Macula densa cells

Granular cellsGranular cells

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3)Renal circulation (22%)

Kidney and urine formation1.Renal structure & function

Autoregulation of RBFConstant 80~180mmHgMyogenic AP AA constriction

AP AA dilation

Neuro humoral regulation of RBF

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Neuro-humoral regulation of RBFSympathetic vasoconstrictor nerveNE, E

Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun6

1)Glomerular Filtration

Kidney and urine formation2.Urine Formation

GFR: 125ml/min(180L/day) (Ultrafiltration)

Filtration membrane Kf

Effective filtration pressure=glomerular capillary ~ -

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(plasma colloid osmotic ~ +capsular pressure)

Afferent end=55-(30+15)=10mmHg

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun7

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun8

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2)Tubular reabsorption and secretion

Kidney and urine formation2.Urine formation

Primary Active transportation Secondary active transportation

i T i180L/day 1.5L/day

i.Proximal tubuleReabsorption:

67% Na+,Cl-,K+,H2O; 85% HCO3-; all glucose, aa

Secretion: H+ H+ -Na+ exchangeii Loop henle

passive Transportation

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ii.Loop henleDescending thin limbH2O passive reabsorption through tight junctionAscending limb Impermeable to H2O ; Na+-2Cl--K+symporter

Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun9

iii.Distal tubule &collecting ductIonic balance & water balance

Kidney and urine formation2.Urine formation (2)Tubular reabsorption and secretion

Early part of the distal tubuleImpermeable to H2O; Active reabsorption NaClLater part ~ & collecting ducts

② Na+ reabsorption (8% )& K+ secretion

① H+ secretion (Intercalated cells) (Acid-base balance)

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② Na+ reabsorption (8% )& K+ secretion ( Na+,K+ balance)

③H2O reabsorption(10%-15%) (Water balance)

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun10

The reabsorption of glucose in the proximal tubule:Secondary active transportation

19Normal: 125mg/min (100mg/100ml); Tm=375mg/min

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun11

Bicarbonate reabsorption in the proximal tubule:

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The processes responsible for the uptake of Na+ and Cl- in the thick ascending limb of the loop of Henle tubule:

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun12

Secretion of H+ by the intercalated cells of distal tubule and collecting ducts:

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The tubule secretion of K+ in the distal tubule and collecting duct:

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun13

Na+

Renin secrection Renin secrection

Angiotension II, III production

Aldosterone release

Na+ channel(P cells) Na+,K+-ATPase

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Na channel(P cells) Na ,K ATPase

Na+reabsorption K+secrection

Na+Na+

ANP (Atrial natriuretic peptide)

Na+ excretion

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun14

The control of H2O uptake by ADH in the distal tubule and collecting duct:

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+

Plasma crystal osmotic pressure

Osmoreceptor

Blood volume

Barorecptor

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+ Osmoreceptor

ADH secretion

Urine volume

Vagus nerve

Center

Symp. nerve Vagus nerve

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_

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Blood volumeOsmotic pressure

Vagus nerve

Blood pressure

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun15

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30Water diuresis

Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun16

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3.Urinary Concentration and Dilution

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600Out medulla: NaCl

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Inner medulla: Urea, NaCl

High ADH Many Water Channels

Low ADH Few Water Channels

Cortex

Collecting Duct

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Medulla

Small Volume Concentrated Urine

Large Volume Dilute Urine

Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun17

Mechanism of countercurrent multiplication:Descending limb:1. Highly

permeable to H2O

2 Not reabsorb 2. Not reabsorb Na+

Ascending limb:1. actively

transports NaCl

2. always

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Impermeable to H2O

Role of vasa recta for maintaining the highsolute concentration of renal medulla

Countercurrent exchange

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Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun18

4 Regulation of Urine formation Kidney and urine formation

4.Regulation of Urine formation (negative feedback)

1)ADH (Antidiuretic hormone )2)Renin-angiotensin-aldosterone system

Na+-conserving system

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4)ANP(Atrial natriuretic peptide)(Atrial myocarial cells) Na+-losing system

3)Renal sympathetic nerves

Volume contraction

Sympathetic activityRenin

ANPAngiotensin II

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Na+,H2OexcretionADH Aldosterone

Human and Animal Physiology; Renal Physiology May, 2009

©2009, Yingyu Sun19

Volume expansion

Sympathetic activityRenin

ANP

Angiotensin II

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Na+,H2OexcretionADH Aldosterone