urinary tract physiologykul.ppt

7/28/2019 Urinary tract physiologyKul.ppt

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Urinary tract physiology

Suyasning HI

[email protected]


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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


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.


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


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+


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-


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


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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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+


lumen


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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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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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6/16/2013 69

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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