The Kidneys

POWERPOINT® LECTURE SLIDE PRESENTATIONby LYNN CIALDELLA, MA, MBA, The University of Texas at AustinAdditional text by J Padilla exclusively for Physiology 31 at ECC

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

HUMAN PHYSIOLOGYAN INTEGRATED APPROACH FOURTH EDITION

DEE UNGLAUB SILVERTHORN

UNIT 3UNIT 3

PART A

19The Kidneys


Functions of the Kidneys

Regulation of extracellular fluid volume and blood pressure - works with CV system to ensure tissues get enough oxygen and BP is within normal values

Regulation of osmolarity – blood osmolarity needs to be maintained around 290mOsM

Maintenance of ion balance - in response to diet urinary loss helps to maintain proper levels of Na+, K+, Ca 2+ .

Homeostatic regulation of pH – they remove either H+ or HCO3- as needed, they don’t correct pH imbalances as effectively as the lungs

Excretion of wastes – removes waste molecules dissolved in the plasma like urea (from amino acid breakdown), uric acid (nucleic acid turnover), and creatine (from creatine phosphate breakdown).

Production of hormones – erythropoietin (signal RBC production), renin (influence BP and BV), and vitamin D conversion to control Ca 2+ .


Anatomy: The Urinary System

Figure 19-1a

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-1c


Cortico & juxtamedullary nephronsCortico & juxtamedullary nephrons

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-1d–e


Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-1g–h


Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-1f


Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-2 (1 of 4)

Kidney Function

Efferentarteriole

Afferentarteriole

Glomerulus

Peritubular capillaries

Proximaltubule

Bowman’scapsule

Collectingduct

To renal vein

F

F

Loopof

Henle = Filtration: blood to lumen

KEY

Distaltubule


Kidney Function

Efferentarteriole

Afferentarteriole

Glomerulus


Proximaltubule

Bowman’scapsule

Collectingduct

To renal vein

F

R

F

R

R R

R

R

Loopof


= Reabsorption: lumen to blood

KEY

Distaltubule


Kidney Function

Efferentarteriole

Afferentarteriole

Glomerulus


Proximaltubule

Bowman’scapsule

Collectingduct

To renal vein

F

R

S

F

R

S

R R

R

S

R S

Loopof



= Secretion: blood to lumen

KEY

Distaltubule


Kidney Function

Efferentarteriole

Afferentarteriole

Glomerulus


Proximaltubule

Bowman’scapsule

Collectingduct

To renal vein

F

R

S

E

F

R

S

R R

R

S

R S

E

Loopof

Henle

To bladder andexternal environment

= Filtration: blood to lumen


= Secretion: blood to lumen

= Excretion: lumen to external environment

KEY

Distaltubule

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-3

Kidney Function

The urinary excretion of substance depends on its filtration, reabsorption, and secretion


Filtration Fraction


Filtration at the glomerulus

Podocytes wrap around fenestrated capilaries creating filtration slits at the glomerulus.


Forces that Influence Filtration

Hydrostatic pressure (blood pressure) – pressure of flowing blood in glomerular capillaries is 55mmHg, it favors the movement of filtrate into Bowman’ Capsule

Colloid osmotic pressure –Plasma proteins that enter the capsule create a gradient the favors movement back into the capillaries

Fluid pressure created by fluid in Bowman’s capsule – The fluid build-up in the enclosed capsule creates a gradient that favors movement back into the capillaries

The combination of these factors causes filtration to return plasma into the capillaries and allow for only 20% of the filtered plasma to move along the tubules.


Filtration

Filtration pressure in the renal corpuscle depends on hydrostatic pressure, colloid osmotic pressure, and fluid pressure


Filtration

Autoregulation of glomerular filtration rate takes place over a wide range of blood pressure


Glomerular Filtration Rate Changes GFR is controlled by a myogenic response,tubuloglomerular feedback,hormones and autonomic neurons

Changing resistance in arterioles altes the filtration coefficient

GFR is controlled by a myogenic response,tubuloglomerular feedback,hormones and autonomic neurons

Changing resistance in arterioles altes the filtration coefficient


Juxtaglomerular Apparatus

Juxtaglomerular cells and Macula densa monitor blood flow and blood pressure along the arteioles. They send chemical signals needed to restore the proper filtration rate

Juxtaglomerular cells and Macula densa monitor blood flow and blood pressure along the arteioles. They send chemical signals needed to restore the proper filtration rate

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10, steps 1–2

Tubuloglomerular Feedback

Afferentarteriole

Maculadensa

Efferent arteriole Bowman’s capsule GlomerulusDistal tubuleProximal

tubule

Collectingduct

Loopof

Henle

Granularcells

GFR increases.

Flow through tubule increases.

2

1

1

2

2

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10, steps 1–4


Afferentarteriole

Maculadensa


tubule

Collectingduct

Loopof

Henle

Granularcells

GFR increases.


Flow past macula densaincreases.

Paracrine diffuses from macula densa to afferent arteriole.

2

1

1

2

3

42

3

4

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10, steps 1–5 (2 of 4)


Afferentarteriole

Maculadensa


tubule

Collectingduct

Loopof

Henle

Granularcells

GFR increases.




Afferent arteriole constricts.

Resistance in afferent arteriole increases.

2

1

1

2

3

4

5

23

4

5

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-10, steps 1–5 (4 of 4)


Afferentarteriole

Maculadensa


tubule

Collectingduct

Loopof

Henle

Granularcells

GFR increases.




Afferent arteriole constricts.

Resistance in afferent arteriole increases.

Hydrostatic pressurein glomerulus decreases.

GFR decreases.

2

1

1

2

3

4

5

23

4

5


ReabsorptionPrinciples governing the tubular reabsorption of solutes and water.

Sodium and water always follow each other.Transepithelial transport- (passing through cells)-Substances cross both apical and basolateral membraneParacellular pathway (passing around cells)-Substances pass through the junction between two adjacent cells

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. Permeablesolutes are reabsorbedby diffusion.

Na+

Anions

H2O

K+, Ca2+,urea

Tubularepithelium Extracellular fluidTubule lumen

Filtrate is similar to interstitial fluid.

1

2

3

4

1

2

3

4


Reabsorption

Saturation of mediated transport

Transport rate is proportional to plasma concentration until transport saturation=renal threshold

Transport rate is proportional to plasma concentration until transport saturation=renal threshold

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15a

Reabsorption

Glucose handling by the nephron

This graph does not show saturation at Bowman’s capsule

This graph does not show saturation at Bowman’s capsule

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15b

Reabsorption

Saturation is reached within the proximal tubule

Saturation is reached within the proximal tubule

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15c

Reabsorption

Excretion rate shows that no glucose is excreted with when plasma glucose concentration is low.

Excretion rate shows that no glucose is excreted with when plasma glucose concentration is low.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-15d

Reabsorption Glucose is not secreted

When filtration and reabsoption are equal and below threshold there is no secretion. Above that results in glucosuria or glycosuria

Glucose is not secreted

When filtration and reabsoption are equal and below threshold there is no secretion. Above that results in glucosuria or glycosuria


Secretion

Transfer of molecules from extracellular fluid into lumen of the nephron - dependent on membrane transport proteins to move organic compounds Active process – move against concentration gradient

and use secondary active transport to move into lumen Secretion of K+ and H+ is important in

homeostatic regulation Enables the nephron to enhance excretion of a

substance – adds to the substances collected during filtration, making excretion more effective

Competition decreases penicillin secretion – doctors combined probenecid with penicillin so it would compete for the transporter protein and keep the kidneys from clearing penicillin so quickly.


Excretion

Excretion = filtration – reabsorption + secretion

Clearance Rate at which a solute disappears from the body by

excretion or by metabolism

Non-invasive way to measure GFR

Inulin and creatinine used to measure GFR


Inulin Clearance

Glomerulus

Peritubularcapillaries

Afferentarteriole

Nephron

Filtration(100 mL/min)

100 mL,0% inulin

reabsorbed

Inulin clearance = 100 mL/min

= 100 mL of plasma or filtrate

100% inulinexcreted

Inulin concentration is 4/100 mL

GFR = 100 mL /min

100 mL plasma is reabsorbed. No inulin is reabsorbed.

100% of inulin is excreted so inulin clearance = 100 mL/min

KEY

Inulinmolecules

Efferentarteriole

1

2

3

4

1

2

3

4

Inulin=polysaccharide; 100% of it is excreted so it is used to measure glomerular filtration rate

Clearance is the rate at which a solute disappears from

the body

Inulin=polysaccharide; 100% of it is excreted so it is used to measure glomerular filtration rate

Clearance is the rate at which a solute disappears from

the body


Excretion


Excretion

The relationship between clearance and excretion is that clearance is the rate of excretion. Different substance have difference clearance.

The relationship between clearance and excretion is that clearance is the rate of excretion. Different substance have difference clearance.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-18a

Micturition

The storage of urine and the micturition reflex

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19-18b

Micturition

Stretch receptors fire.

Stretch receptors

Parasympathetic neurons fire.Motor neurons stop firing.

Smooth muscle contracts.Internal sphincter passively pulled open. External sphincter relaxes.

(b) Micturition

Internalsphincter

Externalsphincter

Tonicdischargeinhibited

Sensory neuron

Parasympatheticneuron

Motor neuron

–

+

Higher CNSinput may

facilitate orinhibit reflex.

1 2 3

1

2

3

23

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The Kidneys

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