The Urinary System

1
Chapter 26
The Urinary System
2
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
3
Major organs
kidneys (2) urinary tract ureters (2) urinary
bladder (1) urethra (1)
produce urine water, soluble compounds kidney
to urinary bladder temporary storage of
urine urinary bladder to exterior
4
Other important functions
regulate blood volume and pressure regulate
ions in blood Na, K, Cl-, etc., stabilize
blood pH conserve nutrients while getting rid of
wastes detoxify compounds
5
kidney location
fig. 26-2
fig. 26-2a
6
The Kidneys
location on either side of vertebral
column around T12 to L3 capped by adrenal
gland retroperitoneal supported by CT surrounded
by adipose (cushioning)
7
to here 4/4/07 lec 35
8
The Kidneys
anatomy
hilum indentation entry/exit ureters renal
artery, vein, nerves
9
fig. 26-4a
10
The Kidneys
anatomy
nephrons
renal cortex renal medulla renal pyramids minor
calyx major calyx renal pelvis
tubular functional numerous vascular
11
The Kidneys
blood supply
20-25 of cardiac output
renal artery segmental artery interlobar
artery arcuate artery
12
kidney vasculature
fig. 26-5a
13
fig. 26-5a
14
The Kidneys
blood supply
coming off of arcuate arteries interlobular
arteries afferent arteriole glomerulus
efferent arteriole peritubular
capillary interlobular veins
arcuate veins
15
fig. 26-5a
16
The nephron overview
renal corpuscle
renal tubule
renal tubule
renal corpuscle
fig 26-6
17
The nephron parts
fig. 26-6a
18
fig. 26-9
19
The nephron blood supply
efferent arteriole
?
glomerulus (capillary bed)
afferent arteriole
fig. 26-6a
20
The nephron blood supply
peritubular capillaries
efferent arteriole
glomerulus (capillary bed)
afferent arteriole
fig. 26-6a
21
The nephron Bowmans capsule
hollow structure two layers visceral
(inner) parietal (outer) surrounds glomerulus
fig 26-6a
22
The nephron Bowmans capsule
fig. 26-8
23
What is between blood and space?
podocytes and filtration slits lamina densa
(connective tissue) fenestrated endothelium
(capillary)
24
pedicel
pedicel
podocyte 1
filtration slits
25
The nephron Bowmans capsule
fig. 26-8
26
blood
endothelium lamina densa filtration slits
capsular space
filtration membrane
fig. 26-10
27
blood pressure forces water and small solutes
across membrane into Bowmans capsule
fig. 26-10
28
wastes but also water glucose amino
acids vitamins fatty acids etc. glomular
filtrate
fig. 26-10
29
but not cells large plasma proteins
fig. 26-10
30
The nephron proximal convoluted tubule
fig. 26-6a
31
The nephron proximal convoluted tubule
cuboidal cells microvilli reabsorption remove
water, nutrients etc., from the glomerular
filtrate and release them into the peritubular
fluid
32
The nephron loop of Henle
fig. 26-6a
33
The nephron loop of Henle
descending limb thick pumps Na Cl- out of
fluid thin permeable to H2O ascending
limb thin thick
34
The nephron distal convoluted tubule
fig. 26-6a
35
The nephron distal convoluted tubule
active secretion (ions, acids, drugs) selective
reabsorption of Na and Ca2 selective
reabsorption of H2O
36
The nephron distal convoluted tubule
also part of the jg apparatus (JGA)
(juxtaglomerular)
macula densa (DCT) juxtaglomerular cells
(afferent arteriole)
secrete EPO, renin
37
juxtaglomerular apparatus
38
The collecting system
DCT

39
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.
40
Renal Physiology
what is the kidney doing how does it accomplish
these tasks
Goal
regulate volume and composition of the
blood involves excretion of wastes
41
Renal Physiology
three major organic wastes
urea creatinine uric acid
21g / day from amino acid breakdown 1.8 g /
day from CP breakdown 480 mg / day recycling RNA
N-bases
42
Renal Physiology
three major organic wastes
can be eliminated only when dissolved in urine
(H2O loss)
production of hyperosmotic urine restrict
excessive H2O loss reabsorb useful molecules
43
Renal Physiology steps
1. filtration
blood pressure forcing water and small solutes
(good and bad) from capillaries into capsular
space
44
Renal Physiology steps
2. reabsorption
remove water and many solutes from filtrate by
diffusion, osmosis channel-mediated
diffusion carrier-mediated transport
45
Renal Physiology steps
2. reabsorption
many different proteins involved a cell may have
many functions differential distribution of
proteins transport can be saturated
46
Renal Physiology steps
3. secretion
transport of solutes from body fluids into the
tubular fluid (or filtrate)
47
table 26-2
48
to here 4/11/07 lec 36
49
Filtration
filtration membrane
lets water and small solutes through cells and
plasma proteins stay in capillaries
50
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.
51
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 - 15
35
mm Hg
52
Filtration colloid pressure
blood colloid osmotic pressure (BCOP) proteins
in blood (hyperosmotic) draw water back into
blood 25 mm Hg
53
Filtration filtration pressure (FP)
FP NHP - BCOP
35 - 25
10
mm Hg
importance of blood pressure
20 drop in blood pressure 50mm Hg to 40mm
Hg filtration would stop
54
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
55
Filtration filtration rate (GFR)
affected by filtration pressure (FP) change
FP change GFR
significant factor in FP is blood pressure
56
Filtration filtration rate (GFR)
control of GFR
adequate blood flow to glomerulus adequate
filtration pressure
autoregulation hormonal regulation autonomic
regulation
57
Filtration filtration rate (GFR)
autoregulation
lower bp
afferent arteriole dilate glomerulus dilate effer
ent arteriole constrict
58
Filtration filtration rate (GFR)
autoregulation
higher bp
afferent arteriole contract less blood
in lower GHP
59
Filtration filtration rate (GFR)
hormonal regulation
renin-angiotensin system
renin is released when
drop in bp JG cells stimulated by sym. lower
osmolarity of tubular fluid
60
Filtration filtration rate (GFR)
hormonal regulation
renin
bp?
angiotensin II
constrict afferent art. secretion of
aldosterone thirst secretion of ADH general
vasoconstriction
bp?
61
Filtration filtration rate (GFR)
hormonal regulation
bp?
GFR?
?fluid loss
bp?
?GFR ?Na reabsorption ?urine production
ANP BNP
62
fig. 26-11
63
Filtration filtration rate (GFR)
autonomic (ANS) regulation
sympathetic stimulation
?bp
powerful vasoconstriction of afferent arteriole
?GFR
?bp
64
Filtration filtration rate (GFR)
maximal physical exertion (ie., marathon, etc.,)
blood to muscle less blood to kidney
damage to glomerulus
proteinuria hematuria
65
Renal Physiology reabsorption/secretion
PCT reabsorbs 60-70 of filtrate
peritubular fluid
peritubular capillaries
66
Renal Physiology reabsorption/secretion
PCT
reabsorb organic nutrients active reabsorption of
ions reabsorption of H2O passive reabsorption of
ions secretion
67
Renal Physiology reabsorption/secretion
PCT
reabsorb organic nutrients
99 absorbed before reaching the loop of Henle
facilitated transport cotransport
(carrier proteins)
68
Renal Physiology reabsorption/secretion
PCT
active reabsorption of ions
Na K HCO3-
active transport
(carrier proteins and ATP)
69
Renal Physiology reabsorption/secretion
PCT
reabsorption of H2O
peritubular fluid
filtrate
solutes
osmosis
H2O
70
fig. 26-12
71
Renal Physiology loop of Henle
countercurrent exchange (multiplication)
fluids moving in opposite directions
descending limb
ascending limb
72
Renal Physiology loop of Henle
thin descending limb thick ascending limb
permeable to H2O impermeable to
solutes impermeable to both contains Na Cl-
pumps
73
Renal Physiology loop of Henle
thick ascending limb
contains Na Cl- pumps
pumps ions out of the tubular filtrate into the
peritubular fluid makes peritubular fluid
hyperosmotic
74
ascending limb is not permeable, but has pumps
Na-K/2Cl- transporter
fig 26-13
75
Na-K/2Cl- transporter
hyperosmotic
fig 26-13a
76
Renal Physiology loop of Henle
thick ascending limb
contains Na Cl- pumps
makes peritubular fluid hyperosmotic
as thin, descending limb passes down, H2O
diffuses out making fluid more concentrated
77
which means there are more ions to pump out
permeable to H20, not solutes
that makes tubular fluid more concentrated
fig 26-13
78
positive feedback maintains a hyperosmotic
peritubular fluid
sets up a concentration gradient within the
medulla of the kidney
79
papillary duct is only place permeable to urea
80
to here 4/13 lec 37
81
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
82
Renal Physiology distal convoluted tubule
reabsorption
remove Na and Cl- from filtrate
aldosterone stimulates the Na pumps in some
parts of the DCT
83
fig. 26-14
84
Renal Physiology distal convoluted tubule
secretion
K sodium-potassium exchange
H secreted to raise blood pH HCO3- is produced
(buffer blood)
85
fig. 26-14c
86
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
87
Renal Physiology the collecting system
regulation
aldosterone ADH
activate Na pumps of DCT and collecting
duct controls permeability of collecting duct
to H2O
88
Renal Physiology the collecting system
reabsorption
Na Bicarbonate Urea
aldosterone controlled exchange for K exchange
for Cl- usually diffuses out of lower portion of
collecting duct
89
Renal Physiology the collecting system
secretion
can secrete H to raise pH or bicarbonate to
lower pH
90
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.
91
What happens to all that stuff that has been
reabsorbed and put into the peritubular space?
taken up by the peritubular capillaries and
returned to circulation.
92
Control of water reabsorption
will determine
volume of urine osmotic concentration of urine
93
Control of water reabsorption
85 will occur no matter what
PCT descending limb of loop of Henle
osmosis
94
Control of water reabsorption
remaining 15 is reabsorbed (or not) by the
DCT and the collecting duct
(27 L / day)
95
Control of water reabsorption
DCT and the collecting duct are usually
impermeable to H2O except in the presence of ADH
96
with ADH
no ADH
more, dilute urine
less, concentrated urine
fig. 26-15
97
Control of water reabsorption
diabetes insipdus
underproduction of ADH not enough water
reabsorbed (too much water lost)
98
Control of water reabsorption
diabetes insipdus
flow through tasteless
gt10 liters of urine / day very thirsty
99
Control of water reabsorption
ANP BNP
natriuretic peptides oppose action of ADH
Diuretics drugs that promote H2O loss
reduce blood volume blood pressure ECF
100
Normal Urine
clear sterile yellow odorous
no bacteria urobilin pigment evaporation of small
molecules
ammonia etc., ketones ?
urinalysis
color, appearance, taste, chemical
101
summary
fig. 26-16
102
Urine transport, storage and elimination
fig. 26-4a
fig. 26-7a
103
Urine transport, storage and elimination
collecting duct minor calyx major
calyx renal pelvis ureter
fig. 26-17
104
Urine transport, storage and elimination
ureter urinary bladder
fig. 26-18c
105
Urine transport, storage and elimination
ureter urinary bladder sphincters
(2) urethra urethral opening
106
Urine transport, storage and elimination
fig. 26-18
smooth muscle
107
Urine transport, storage and elimination
fig. 26-18
108
Urine transport, storage and elimination
micturation reflex

1. stretch bladder
2. sense
3. stimulate muscle
4. relax sphincter(s)

109
Urine transport, storage and elimination
micturation reflex
incontinence
inabililty to voluntarily control urination
110
Aging and the urinary system

• decline in of functional nephrons
• reduction in GFR
• (1, reduced blood flow)
• less responsive to ADH
• voiding problems
• loss of muscle tone
• cerebral damage
• bph