urinary tract physiologykul.ppt
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Urinary tract physiology
Suyasning HI
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Composition of the Urinary System
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Out line
1) Urine Formation
2) Urine Storage and Elimination
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afferent arteriole
glomerulus
efferent arteriole
proximal
convoluted
tubule
distal
convoluted
tubule
Loop of Henle
blood
blood
The Nephron
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URINE FORMATION
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The kidney produces urine through 4 steps.
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Glomerular
Filtrate
Tubular fluid
Urine
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Blood cellsin urine
Plasma proteins
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Glomerular Filtration Rate (GFR)
- is the amount of filtrate formed per minuteby the two kidneys combined.
- For the average adult male, GFR is about
125 ml/m in.
- This amounts to a rate of180 L/day.
- An average of99% of the filtrate is
reabsorbed, so that only 1-2 L of urine per
day is excreted.
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GFR must be precisely
controlled.
a. If GFR is too high
- increase in urine output
- threat of dehydration and electrolyte
depletion.
b. If GFR is too low
- insufficient excretion of wastes.
c. The only way to adjust GFR frommoment to moment is to change
glomerular blood pressure.
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Renal Autoregulation
- the ability of the kidneys to maintain arelatively stable GFR in spite of the
changes (75 - 175 mmHg) in arterial
blood pressure.
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The nephron has two ways to
prevent drastic changes in GFR
when blood pressure rises:
1) Constriction of the afferent
arteriole to reduce blood flow into
the glomerulus
2) Dilation of the efferent arteriole
to allow the blood to flow out
more easily.
Change in an opposite direction ifblood pressure falls
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Mechanisms of Renal Autoregulation
1) myogenic response
2) tubuloglomerular feedback
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1) myogenic response
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2) tubuloglomerular feedback
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1) Glomerular Filtration
2) Tubular Reabsorption
3) Tubular Secretion
4) Concentrating Urine by Collecting Duct
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About 99% of Water and
other useful small moleculesin the filtrate are normally
reabsorbed back into
plasma by renal tubules.
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Reabsorption in Proximal
Convoluted Tubules
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- The proximal convolutedtubule (PCT) is formed by
one layer of epithelial cells
with long apical microvilli.
- PCT reabsorbs about
65% of the glomerular
filtrate and return it to the
blood.
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1) transcellular route
2) paracellular route
Routes of Proximal
Tubular Reabsorption
PCT
peritubular capillary
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Mechanisms of Proximal Tubular
Reabsorption
1) Solvent drag
2) Active transport of sodium.
3) Secondary active transport of glucose, amino
acids, and other nutrients.
4) Secondary water reabsorption via osmosis
5) Secondary ion reabsorption via electrostatic
attraction6) Endocytosis of large solutes
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Osmosis
Water moves from a compartment of low osmolarity
to the compartment of high osmolarity.
low osmolarity
( high H2O conc.)
high osmolarity
( low H2O conc.)
H2O
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1) Solvent drag
- driven by highcolloid osmotic
pressure (COP) in the
peritubular capillaries
- Water is reabsorbedby osmosis and
carries all other
solutes along.
- Both routes are
involved.
Proteins stay
H2O
Proteins
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2) Active transport of sodium
Sodium pumps(Na-K ATPase) in basolateral
membranes transport sodium out of the cells against itsconcentration gradient using ATP.
capillary PCT cell Tubular
lumen
Na+
K+
Na+
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There are also pumps for other ions
capillary PCT cell Tubular
lumen
Ca++ Ca++
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- Various cotransporters can carry both Na+ andother solutes. For example, the sod ium-
dependent g lucose transporter(SDGT) can
carry both Na+ and glucose.
3) Secondary active transport of glucose, amino
acids, and other nutrients
Na+
Glucose
capillary PCT cell
Na+
K+
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Amino acids and many other nutrients are
reabsorbed by their specific cotransporters
with sodium.
Na+
capillary PCT cell
Na+
K+
amino acids
3) Secondary active transport of glucose, amino
acids, and other nutrients
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Sodium reabsorption makes bothintracellular and extracellular fluid hypertonic
to the tubular fluid. Water follows sodium into
the peritubular capillaries.
4) Secondary water reabsorption via osmosis
H2O
Na+Na+
capillary PCT cell Tubular
lumen
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Negative ions tend to follow the positive
sodium ions by electrostatic attraction.
5) Secondary ion reabsorption via
electrostatic attraction
Na Na+
Cl-
capillary PCT cell Tubular
lumen
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The glomerulus filters a small amount of protein
from the blood. The PCT reclaims it by endocytos is,hydrolzes it to amino acids, and releases these to the
ECF by facilitated diffusion.
6) Endocytosis of large solutes
protein
capillary PCT cell Tubular
lumen
amino acids
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The Transport Maximum
- There is a limit to the amount of solute that the renal
tubule can reabsorb because there are limited numbers oftransport proteins in the plasma membranes.
- If all the transporters are occupied as solute molecules
pass through, some solute will remain in the tubular fluid
and appear in the urine.
Na+
Glucose
Example of diabetes
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Glucose in urine
high glucose in blood
high glucose in filtrate
Exceeds Tm for glucose
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Reabsorption in the
Nephron Loop
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- The primary purpose
is to establish a high
extracellular osmotic
concentration.
- The thick ascending
limb reabsorbs solutes
but is impermeable towater. Thus, the tubular
fluid becomes very
diluted while
extracellular fluid
becomes very
concentrated with
solutes.mOsm/L
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The high osmolarity enables the collecting duct
to concentrate the urine later.
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Reabsorption in Distal
Convoluted Tubules
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- Fluid arriving in theDCT still contains about
20% of the water and
10% of the salts of the
glomerular filtrate.
- A distinguishing feature
of these parts of the renal
tubule is that they are
subject to hormonalcont ro l.
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Aldosterone
a. secreted from adrenal
gland in response to a
Na+ or a K+ in blood
b. to increase Na+ absorptionand K+ secretion in the DCT
and cortical portion of the
collecting duct.
c. helps to maintain blood
volume and pressure.
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Atr ial Natr iuret ic Facto r
- secreted by the atrialmyocardium in response to
high blood pressure.
- It inhibits sodium and
water reabsorption,increases the output of both
in the urine, and thus
reduces blood volume and
pressure.
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1) Glomerular Filtration
2) Tubular Reabsorption
3) Tubular Secretion
4) Concentrating Urine by Collecting Duct
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Tubular Secretion
- Renal tubule extracts chemicals from the blood and
secretes them into the tubular fluid.
- serves the purposes of waste removal and acid-base
balance.
H+H+
capillary PCT cell Tubular
lumen
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1) Glomerular Filtration
2) Tubular Reabsorption
3) Tubular Secretion
4) Concentrating Urine by Collecting Duct
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1. The collecting duct
(CD) begins in the
cortex, where it
receives tubular fluid
from numerous
nephrons.
2. CD reabsorbs water.
Cortex
collecting
duct
urine
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1. Driving force
The high
osmolar i tyof extracellularfluid generated by NaCl
and urea, provides the
driving force for water
reabsorption.
2. Regulation
The medullary
portion of the CD is not
permeable to NaClbut
permeable to water,
depending on ADH.
Cortex
mOsm/L
medulla
urine
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a. In a state offu l l hyd rat ion,antidiuretic hormone (ADH) is
not secreted and the CD
permeability to water is low,
leaving the water to beexcreted.
Cortex
mOsm/L
medulla
Control of Urine Concentration depends on the
body's state of hydration.
urine
b. In a state ofdehydrat ion,
ADH is secreted; the CD
permeability to waterincreases. With the increased
reabsorption of water by
osmosis, the urine becomes
more concentrated.
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Cortex
medulla
urine
No more reabsorption after tubular fluid leaving CD
urine
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Composition and Properties of Urine
Fresh urine is clear, containing no b lood
cellsand l i t t le pro teins. If cloudy, it could
indicate the presence of bacteria, semen,
blood, or menstrual fluid.
Urine Properties
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Substance Blood Plasma
(total amount)
Urine
(amount per day)
Urea 4.8 g 25 gUric acid 0.15 g 0.8 g
Creatinine 0.03 g 1.6 g
Potassium 0.5 g 2.0 gChloride 10.7 g 6.3 g
Sodium 9.7 g 4.6 g
Protein 200 g 0.1 g
HCO3- 4.6 g 0 g
Glucose 3 g 0 g
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Urine Volume
An average adult produces 1-2 L of urine per
day.
a. Excessive urine output is calledpolyur ia.
b. Scanty urine output is ol igur ia. An
output of less than 400 mL/dayis
insufficient to excrete toxic wastes.
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Urine Storage and Elimination
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The Ureters
The ureters are muscular tubes leading from the
renal pelvis to the lower bladder.
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Urine Movement
Hydrostatic pressure forces urine throughnephron
Peristalsis moves urine through ureters fromregion of renal pelvis to urinary bladder. Occur
from once every few seconds to once every 2-3minutes
Parasympathetic stimulation: increasefrequency
Sympathetic stimulation: decrease frequency
Ureters enter bladder obliquely through trigone.Pressure in bladder compresses ureter andprevents backflow
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The Urinary Bladder
- is a muscular sac on the floor of the pelvic cavity.
- is highly distensible and expands superiorly.
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The openings of the two ureters and the urethra mark a
triangular area called the trigone on the bladder floor.
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The Urethra
- conveys urine from the urinary bladder to the
outside of the body.
Females male
3-4 cm ~18 cm
greater risk of
urinary tract
infections
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The male urethra has three
regions:
1) prostatic urethra
2) membranous urethra
3) penile urethra.
Difficulty in voiding urine
with enlarged prostate
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In both sexes:
- internal urethral sphincter- under involuntary control.
- external urethral sphincter - under voluntary control
internal urethral sphincter
external urethral sphincter
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Neural Control of Micturition
Micturition Reflex
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Micturition Reflex
Sympathetic nerve
Innervation of the
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L1
L2
L3
Sympathetic nerve
supply
Sympatheticchain
Hypogastric
ganglion
Hypogastric
nerve Urethra
External sphincter
Parasympathetic nerve
supply S2
S3
S4
S2S3S4
Pelvic nerve
Pudendal nerve
bladder
Somatic
nerve
supply
S th ti l d I t l th l hi t
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Sympathetic nerve supply and Internal urethral sphincter
apparently play no role in micturition. They prevent reflux of semen
into the bladder during ejaculation.
Parasympathetic nerve supply
Sensory fibers in the pelvic nerve carry impulses from stretch
receptors present on the wall of the urinary bladder to the spinal
centre of micturition. Stimulation of parasympathetic efferent
fibers causes contraction of detrusor muscle leading to emptying
of urinary bladder.
Somatic nerve supply
This maintains the tonic contractions of the skeletal muscle fibers
of the external sphincter, so that this sphincter is contracted
always. During micturition this nerve is inhibited, causing
relaxation of the external sphincter and voiding of urine.
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What is micturition?
Spinal cord reflex activity.
* facilitated or inhibited by higher centers
* voluntary facilitation or inhibition
Voiding Urine in infants
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Spinal
cord
Voiding Urine in infants
mictur i t ion ref lexWhen the bladder contains about 200 ml of urine, stretch receptors in the wall send
impulses to the spinal cord. Parasympathetic signals return to stimulate contractionof the bladder and relaxation of the internal urethral sphincter.
Voiding Urine in adults
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2. Once voluntary control has developed, emptying of the bladder
is controlled predominantly by a micturition center in the pons. This
center receives signals from stretch receptors and integrates this
information with cortical input concerning the appropriateness of
urinating at the moment. It sends back impulses to stimulate
relaxation of the external sphincter.
Once voluntary control has developed, emptying of the
bladder is controlled predominantly by a micturition center
in the pons. This center receives signals from stretch
receptors and integrates this information with cortical input
concerning the appropriateness of urinating at the
moment. It sends back impulses to stimulate relaxation of
the external sphincter.
Voiding Urine in adults
Voluntary
control
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Urine Volume
Normal volume - 1 to 2 L/day
Polyuria > 2L/day Oliguria < 500 mL/day
Anuria - 0 to 100 mL/day
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6/16/2013 66
ISTILAH-ISTILAH YANG BERHUBUNGAN
DENGAN PRODUKSI DAN EKSRESI URIN.
- UN-URIE
- OLIGOURIE
- POLYURIE- DYSURIE
- POLAKISURIE
- INKONTINENSIA URINAE
KELAINAN MIKSI
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6/16/2013 67
KELAINAN MIKSI
1. KK ATONIK AKIBAT KERUSA
KAN SARAF SENSORIK.
-KARENA BENTURAN PD KECELAKAAN
- TABES DORSAL IS : KK TABETIK
2. REFLEX BERKEMIH TERJADI,
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6/16/2013 68
2. REFLEX BERKEMIH TERJADI,
TETAPI TIDAK DIKENLIKAN
OLEH OTAK
BEBERAPA HARI-MINGGU, REFLEX MIKSI
TERTEKAN DISEBUT SYOK SPINAL.
KATETERISASI TERUS DILAKUKAN, SUATU SAAT
REFLEX MIKSI AKAN TIMBUL.
3. OLEH KARENA HAMBATAN
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DARI OTAK TIDAK ADA, MIKSI
MENJADI KESERINGAN
INI OLEH KARENA KERUSAKAN
PARSIAL MED. SPINALIS/ BATANG
OTAK YG MENGGANGGU SEMUA
SINYAL PENGHAMBAT.
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Diuretics
Effects
urine output blood volume
Uses hypertension and congestive heart
failure
Mechanisms of action GFR tubular reabsorption
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SUMMARY
1) Urine Formation
2) Urine Storage and Elimination
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