Download - Chapter 26
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Chapter 26
The Urinary System
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Three major functions:
excretion:
elimination:
regulate blood plasma:
removal of organic wastes from body fluids
discharge of waste products into the environment
volume and solute concentration
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Major organs
kidneys (2)
urinary tract:ureters (2)
urinary bladder (1)
urethra (1)
produce urinewater, soluble compounds
kidney to urinary bladder
temporary storage of urine
urinary bladder to exterior
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regulate blood volume and pressure
regulate [ions] in bloodNa+, K+, Cl-, etc.,
stabilize blood pH
conserve nutrientswhile getting rid of wastes
detoxify compounds
Other important functions:
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kidney location
fig. 26-2a
fig. 26-2
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The Kidneys
location
on either side of vertebral columnaround T12 to L3capped by adrenal glandretroperitonealsupported by CTsurrounded by adipose (cushioning)
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to here 4/4/07lec# 35
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The Kidneys
anatomy:
hilum indentationentry/exit
uretersrenal artery, vein, nerves
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fig. 26-4a
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The Kidneys
anatomy:
renal cortexrenal medullarenal pyramidsminor calyxmajor calyxrenal pelvis
nephronstubularfunctionalnumerousvascular
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The Kidneys
blood supply
20-25% of cardiac output
renal artery
segmental artery
interlobar artery
arcuate artery
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kidney vasculature
fig. 26-5a
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fig. 26-5a
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The Kidneys
blood supply
coming off of arcuate arteries interlobular arteries afferent arteriole glomerulus efferent arteriole peritubular capillary interlobular veins arcuate veins
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fig. 26-5a
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The nephron overview
renaltubule renal
corpuscle
renalcorpuscle
renaltubule
fig 26-6
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fig. 26-6a
The nephron:partsBowman’s
capsule
Bowman’scapsule
proximalconvoluted
tubulepct
loop ofHenle
loop o
f H
enle
distalconvoluted
tubule
dct
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fig. 26-9
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fig. 26-6a
The nephron:blood supply
afferentarteriole
efferentarteriole
glomerulus(capillary bed)
?
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afferentarteriole
efferentarteriole
glomerulus(capillary bed)
fig. 26-6a
The nephron:blood supply
peritubularcapillaries
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The nephron: Bowman’s capsule
fig 26-6a
hollow structuretwo layers
visceral (inner)parietal (outer)
surrounds glomerulus
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fig. 26-8
The nephron: Bowman’s capsule
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What is between blood and space?
podocytes and filtration slits
lamina densa (connective tissue)
fenestrated endothelium (capillary)
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filtration slits
podocyte 1
podocyte 2
pedicel
pedicel
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fig. 26-8
The nephron: Bowman’s capsule
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fig. 26-10
endotheliumlamina densafiltration slits
= filtration membrane
blood
capsular space
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fig. 26-10
blood pressure forces water and small solutes across “membrane” into Bowman’s capsule
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wastes
but also
waterglucose
amino acidsvitamins
fatty acidsetc.
= glomular filtrate
fig. 26-10
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fig. 26-10
but not:
cellslarge plasma proteins
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fig. 26-6a
proximalconvoluted
tubulepct
The nephron: proximal convoluted tubule
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The nephron: proximal convoluted tubule
cuboidal cellsmicrovillireabsorption
remove water, nutrients etc., from the glomerular filtrate and release them into the peritubular fluid
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fig. 26-6a
loop ofHenle
loop o
f H
enle
The nephron: loop of Henle
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The nephron: loop of Henle
descending limbthick pumps Na+ Cl- out of
fluidthin permeable to H2O
ascending limbthinthick
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fig. 26-6a
The nephron: distal convoluted tubule
distalconvoluted
tubule
dct
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The nephron: distal convoluted tubule
active secretion (ions, acids, drugs)
selective reabsorption of Na+ and Ca2+
selective reabsorption of H2O
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The nephron: distal convoluted tubule
also part of the jg apparatus (JGA)
(juxtaglomerular)
macula densa (DCT)juxtaglomerular cells (afferent arteriole)
secrete EPO, renin
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juxtaglomerular apparatus
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The collecting system
DCT
collecting duct
papillary duct
minor calyx
…
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100 keys (pg. 959)
“The kidneys remove waste products from the blood; they also assist in the regulation of blood volume and blood pressure, ion levels, and blood pH. Nephrons are the primary functional units of the kidneys.”
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Renal Physiology
what is the kidney doinghow does it accomplish these tasks
Goal regulate volume and composition of the blood
involves excretion of wastes
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Renal Physiology
three major organic wastes
urea
creatinine
uric acid
21g / dayfrom amino acid breakdown
1.8 g / dayfrom CP breakdown
480 mg / dayrecycling RNA N-bases
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Renal Physiology
three major organic wastes
can be eliminated only when dissolved in urine (H2O loss)
production of hyperosmotic urinerestrict excessive H2O lossreabsorb useful molecules
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Renal Physiology: steps
1. filtration
blood pressure forcing water and small solutes (good and bad) from capillaries into capsular space
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Renal Physiology: steps
2. reabsorption
remove water and many solutes from filtrate by:
diffusion, osmosischannel-mediated diffusioncarrier-mediated transport
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Renal Physiology: steps
2. reabsorption
many different proteins involveda cell may have many functionsdifferential distribution of proteinstransport can be saturated
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Renal Physiology: steps
3. secretion
transport of solutes from body fluids into the tubular fluid (or filtrate)
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table 26-2
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to here 4/11/07lec# 36
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Filtration
filtration membrane
lets water and small solutes through
cells and plasma proteins stay in capillaries
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100 keys (pg. 969)
“Roughly 180 L of filtrate is produced at the glomeruli each day, and that represents 70 times the total plasma volume. Almost all of that fluid volume must be reabsorbed to avoid fatal dehydration.”
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Filtration: hydrostatic pressure
glomerular hydrostatic pressure (GHP)push fluid out of vessels (bp)
capsular hydrostatic pressure (CsHP)push fluid back into vessels
net hydrostatic pressure (NHP)
NHP = GHP - CsHP
50 - 1535 = mm Hg
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Filtration: colloid pressure
blood colloid osmotic pressure (BCOP)
proteins in blood (hyperosmotic)
draw water back into blood
~ 25 mm Hg
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Filtration: filtration pressure (FP)
FP = NHP - BCOP
35 - 2510 = mm Hg
importance of blood pressure
20% drop in blood pressure50mm Hg to 40mm Hg
filtration would stop
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Filtration: filtration rate (GFR)
glomerular filtration rate (GFR)
amount of fluid pushed into the capsular space each minute
GFR ~ 125 ml / min
180 liters (~50 gallons)/ day
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Filtration: filtration rate (GFR)
affected by filtration pressure (FP)
change FP
change GFR
significant factor in FP is…… blood pressure
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Filtration: filtration rate (GFR)
control of GFR
adequate blood flow to glomerulusadequate filtration pressure
autoregulationhormonal regulationautonomic regulation
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Filtration: filtration rate (GFR)
autoregulation
lower bp
afferent arteriole dilateglomerulus dilateefferent arteriole constrict
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Filtration: filtration rate (GFR)
autoregulation
higher bp
afferent arteriole contractless blood in
lower GHP
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Filtration: filtration rate (GFR)
hormonal regulation
renin-angiotensin system
renin is released when:
drop in bpJG cells stimulated by sym.lower osmolarity of tubular fluid
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Filtration: filtration rate (GFR)
hormonal regulation
renin
angiotensin II
constrict afferent art.secretion of aldosteronethirstsecretion of ADHgeneral vasoconstriction
bp
bp
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Filtration: filtration rate (GFR)
hormonal regulation
fluid loss
bp
bp
GFR
ANPBNP
GFRNa+ reabsorptionurine production
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fig. 26-11
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Filtration: filtration rate (GFR)
autonomic (ANS) regulation
sympathetic stimulation
powerful vasoconstrictionof afferent arteriole
GFR
bp
bp
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Filtration: filtration rate (GFR)
maximal physical exertion(ie., marathon, etc.,)
blood to muscleless blood to kidney
proteinuriahematuria
damage to glomerulus
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Renal Physiology: reabsorption/secretion
PCT reabsorbs 60-70% of filtrate
peritubularfluid
peritubularcapillaries
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Renal Physiology: reabsorption/secretion
PCT reabsorb organic nutrientsactive reabsorption of ionsreabsorption of H2Opassive reabsorption of ionssecretion
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Renal Physiology: reabsorption/secretion
PCT reabsorb organic nutrients
99% absorbed before reaching the loop of Henle
facilitated transportcotransport
(carrier proteins)
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Renal Physiology: reabsorption/secretion
PCT active reabsorption of ions
Na+
K+
HCO3-
active transport
(carrier proteins and ATP)
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Renal Physiology: reabsorption/secretion
PCT reabsorption of H2O
solutesH2O
filtrate
osmosis
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fig. 26-12
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Renal Physiology: loop of Henle
countercurrent exchange (multiplication)
fluids moving in opposite directions
descendinglimb
ascendinglimb
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Renal Physiology: loop of Henle
thin descending limb
thick ascending limb
permeable to H2Oimpermeable to solutes
impermeable to bothcontains Na+ + Cl- pumps
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Renal Physiology: loop of Henle
thick ascending limb
contains Na+ + Cl- pumps
pumps ions out of the tubular filtrateinto the peritubular fluid
makes peritubular fluid hyperosmotic
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fig 26-13
ascending limb is not permeable, but has pumps
Na+-K+/2Cl-
transporter
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fig 26-13a
Na+-K+/2Cl-
transporter
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Renal Physiology: loop of Henle
thick ascending limb
contains Na+ + Cl- pumps
makes peritubular fluid hyperosmoticas thin, descending limb passes down, H2O diffuses out making fluid more concentrated
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fig 26-13
permeable to H20,not solutes
that makes tubular fluid more concentrated
which means there are more ions to pump out
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positive feedback maintains a hyperosmotic peritubular fluid
sets up a concentration gradient within the medulla of the kidney
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papillary duct is only place permeable to urea
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to here 4/13lec # 37
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Renal Physiology: distal convoluted tubule
only 15-20% of original volume of filtrate makes it to the DCT
final adjustments are made here:
reabsorption
secretion
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Renal Physiology: distal convoluted tubule
reabsorption
remove Na+ and Cl- from filtrate
aldosterone stimulates the Na+ pumps in some parts of the DCT
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fig. 26-14
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Renal Physiology: distal convoluted tubule
secretion
K+ sodium-potassium exchange
H+ secreted to raise blood pHHCO3
- is produced (buffer blood)
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fig. 26-14c
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Renal Physiology: the collecting system
reabsorption and secretion
collecting ducts gather tubular fluid from many nephrons and transport it toward the ureter through the concentration gradient set up in the medulla
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Renal Physiology: the collecting system
regulation
aldosterone
ADH
activate Na+ pumps of DCT and collecting duct
controls permeability of collecting duct to H2O
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Renal Physiology: the collecting system
reabsorption
Na+
Bicarbonate
Urea
aldosterone controlledexchange for K+
exchange for Cl-
usually diffuses out of lower portion of collecting duct
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Renal Physiology: the collecting system
secretion
can secrete H+ to raise pHor
bicarbonate to lower pH
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100 keys (pg. 976)
“Reabsorption involves a combination of diffusion, osmosis, channel-mediated diffusion, and active transport. Many of these processes are independently regulated by local or hormonal mechanisms. the primary mechanism governing water reabsorption can be described as “water follows salt.” Secretion is a selective, carrier-mediated process.”
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What happens to all that stuff that has been reabsorbed and put into the peritubular space?
taken up by the peritubular capillariesand returned to circulation.
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Control of water reabsorption
will determine:
volume of urineosmotic concentration of urine
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Control of water reabsorption
85% will occur no matter what
PCTdescending limb of loop of Henle
osmosis
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Control of water reabsorption
remaining 15% is reabsorbed (or not) by the DCT
and the collecting duct
(27 L / day)
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Control of water reabsorption
DCT and the collecting duct are usually impermeable to H2O
except in the presence of ADH
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fig. 26-15
no ADH with ADH
more, dilute urine less, concentrated urine
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Control of water reabsorption
diabetes insipdus
underproduction of ADH
not enough water reabsorbed(too much water lost)
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Control of water reabsorption
diabetes insipdusflow through tasteless
>10 liters of urine / dayvery thirsty
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Control of water reabsorption
ANPBNP
natriuretic peptidesoppose action of ADH
Diuretics: drugs that promote H2O loss
reduce blood volumeblood pressureECF
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Normal Urine
clearsterileyellowodorous
urinalysis
no bacteriaurobilin pigmentevaporation of small molecules
ammonia etc.,ketones ?
color, appearance, taste, chemical
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fig. 26-16
sum
mary
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Urine transport, storage and eliminationfig. 26-4afig. 26-7a
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Urine transport, storage and elimination
collecting ductminor calyx
major calyxrenal pelvis
ureter
fig. 26-17
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Urine transport, storage and elimination
ureterurinary bladder
fig. 26-18c
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Urine transport, storage and elimination
ureterurinary bladder
sphincters (2)urethra
urethral opening
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Urine transport, storage and eliminationfig. 26-18
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Urine transport, storage and eliminationfig. 26-18
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Urine transport, storage and elimination
micturation reflex
1. stretch bladder2. sense3. stimulate muscle4. relax sphincter(s)
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Urine transport, storage and elimination
micturation reflex
incontinence
inabililty to voluntarily control urination
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Aging and the urinary system
1. decline in # of functional nephrons2. reduction in GFR
(#1, reduced blood flow)3. less responsive to ADH4. voiding problems
loss of muscle tonecerebral damagebph