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POWERPOINT® LECTURE SLIDE PRESENTATION
by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin
Additional text by J Padilla exclusively for Physiology 31 at ECC
UNIT 3
19
PART A
The Kidneys
HUMAN PHYSIOLOGY
AN INTEGRATED APPROACH
DEE UNGLAUB SILVERTHORN
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FOURTH EDITION
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+ Copyright
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.
Anatomy: The Urinary System
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Figure 19-1a
Anatomy: The Urinary System
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Cortico & juxtamedullary
nephrons
Figure 19-1c
Anatomy: The Urinary System
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Figure 19-1d–e
Anatomy: The Urinary System
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Figure 19-1g–h
Anatomy: The Urinary System
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Figure 19-1f
Kidney Function
Peritubular capillaries
Distal
tubule
Efferent
arteriole
Glomerulus
F
Afferent
arteriole
Bowman’s
capsule
KEY
F
= Filtration: blood to lumen
Proximal
tubule
Loop
of
Henle
Collecting
duct
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To
renal
vein
Figure 19-2 (1 of 4)
Kidney Function
Peritubular capillaries
Distal
tubule
Efferent
arteriole
R
Glomerulus
F
R
Afferent
arteriole
Bowman’s
capsule
Proximal
tubule
R
R
KEY
F
= Filtration: blood to lumen
R
= Reabsorption: lumen to blood
R
Loop
of
Henle
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Collecting
duct
To
renal
vein
Figure 19-2 (2 of 4)
Kidney Function
Peritubular capillaries
Efferent
arteriole
Distal
tubule
S
R
Glomerulus
F
R
Afferent
arteriole
Bowman’s
capsule
S
Proximal
tubule
R
S
R
KEY
F
= Filtration: blood to lumen
R
= Reabsorption: lumen to blood
S
= Secretion: blood to lumen
R
Loop
of
Henle
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Collecting
duct
To
renal
vein
Figure 19-2 (3 of 4)
Kidney Function
Peritubular capillaries
Efferent
arteriole
Distal
tubule
S
R
Glomerulus
F
R
Afferent
arteriole
Bowman’s
capsule
S
Proximal
tubule
R
S
R
KEY
F
= Filtration: blood to lumen
R
= Reabsorption: lumen to blood
S
= Secretion: blood to lumen
R
Loop
of
Henle
To
renal
vein
Collecting
duct
E
E
= Excretion: lumen to external
environment
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To bladder and
external environment
Figure 19-2 (4 of 4)
Kidney Function
The urinary excretion of substance depends on its
filtration, reabsorption, and secretion
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Figure 19-3
Filtration Fraction
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Figure 19-5
Filtration at the glomerulus
 Podocytes
wrap
around
fenestrated
capilaries
creating
filtration
slits at the
glomerulus
.
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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.
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Filtration
Filtration pressure in the renal corpuscle depends on
hydrostatic pressure, colloid osmotic pressure, and
fluid pressure
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Figure 19-6
Filtration
Autoregulation of glomerular filtration rate takes place
over a wide range of blood pressure
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Figure 19-7
Glomerular Filtration Rate Changes
GFR is
controlled by a
myogenic
response,
tubuloglomeru
lar feedback,
hormones and
autonomic
neurons
Changing
resistance
in
arterioles
altes the
filtration
coefficient
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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
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Figure 19-9
Tubuloglomerular Feedback
Distal tubule
Efferent arteriole
Bowman’s capsule
Macula
densa
Glomerulus
Proximal
tubule
1 GFR increases.
2 Flow through tubule increases.
1
Afferent
arteriole
Granular
cells
2
Collecting
duct
Loop
of
Henle
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Figure 19-10, steps 1–2
Tubuloglomerular Feedback
Distal tubule
Efferent arteriole
Bowman’s capsule
Macula
densa
Granular
cells
1 GFR increases.
2 Flow through tubule increases.
4
Afferent
arteriole
Glomerulus
Proximal
tubule
1
3 Flow past macula densa
increases.
3
2
4 Paracrine diffuses from macula
densa to afferent arteriole.
Collecting
duct
Loop
of
Henle
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Figure 19-10, steps 1–4
Tubuloglomerular Feedback
Distal tubule
Efferent arteriole
Bowman’s capsule
Macula
densa
Glomerulus
Proximal
tubule
1 GFR increases.
2 Flow through tubule increases.
4
1
5
Afferent
arteriole
Granular
cells
3 Flow past macula densa
increases.
3
2
4 Paracrine diffuses from macula
densa to afferent arteriole.
5 Afferent arteriole constricts.
Resistance in afferent
arteriole increases.
Collecting
duct
Loop
of
Henle
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Figure 19-10, steps 1–5 (2 of 4)
Tubuloglomerular Feedback
Distal tubule
Efferent arteriole
Bowman’s capsule
Macula
densa
Glomerulus
Proximal
tubule
1 GFR increases.
2 Flow through tubule increases.
4
1
5
Afferent
arteriole
Granular
cells
3 Flow past macula densa
increases.
3
2
4 Paracrine diffuses from macula
densa to afferent arteriole.
5 Afferent arteriole constricts.
Resistance in afferent
arteriole increases.
Collecting
duct
Loop
of
Henle
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Hydrostatic pressure
in glomerulus decreases.
GFR decreases.
Figure 19-10, steps 1–5 (4 of 4)
Reabsorption
Principles 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
1 Na+ is reabsorbed
by active transport.
Filtrate is
similar to
interstitial fluid.
1 Na+
2 Electrochemical
gradient drives
anion reabsorption.
2 Anions
3 Water moves by
osmosis, following
solute reabsorption.
3 H2O
4 K+, Ca2+,
urea
Tubule lumen
Tubular
epithelium
Extracellular fluid
4 Concentrations of
other solutes increase
as fluid volume in lumen
decreases. Permeable
solutes are reabsorbed
by diffusion.
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Figure 19-11
Reabsorption
Saturation of mediated transport
Transport rate
is proportional
to plasma
concentration
until transport
saturation=ren
al threshold
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Figure 19-14
Reabsorption
Glucose handling by the nephron
This graph does
not show
saturation at
Bowman’s capsule
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Figure 19-15a
Reabsorption
Saturation
is reached
within the
proximal
tubule
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Figure 19-15b
Reabsorption
Excretion rate
shows that no
glucose is
excreted with
when plasma
glucose
concentration
is low.
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Figure 19-15c
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
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Figure 19-15d
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.
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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
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Inulin Clearance
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
Efferent
arteriole
Filtration
(100 mL/min)
Glomerulus
Peritubular
capillaries
2
Afferent
arteriole
1
Inulin
molecules
Nephron
KEY
the body
= 100 mL of plasma or filtrate
1
Inulin concentration is 4/100 mL
2
GFR = 100 mL /min
3
100 mL plasma is reabsorbed.
No inulin is reabsorbed.
4
100% of inulin is excreted so
inulin clearance = 100 mL/min
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3
100% inulin
excreted
100 mL,
0% inulin
reabsorbed
4 Inulin clearance
= 100 mL/min
Figure 19-16
Excretion
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Excretion
The
relationship
between
clearance and
excretion is
that clearance
is the rate of
excretion.
Different
substance
have
difference
clearance.
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Micturition
The storage of urine and the micturition reflex
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Figure 19-18a
Micturition
1
(b)
Stretch receptors fire.
2
Parasympathetic neurons fire.
Motor neurons stop firing.
3
Smooth muscle contracts.
Internal sphincter passively
pulled open. External
sphincter relaxes.
Micturition
Stretch
receptors
Higher CNS
input may
facilitate or
inhibit reflex.
Sensory neuron
Parasympathetic
neuron
1
2
3
+
–
Motor neuron
Internal
sphincter
2
3
Tonic
discharge
inhibited
External
sphincter
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Figure 19-18b