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#Micturition The process by which the urinary bladderempties when it become filled This involves two main steps:1. The bladder fills progressively until thetension in its walls rises above a thresholdlevel, which then elicits the second step2. A nervous reflex called the micturition reflex

occurs that empties the bladders or if thisfails, at least causes a conscious desire tourinate

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-The micturition reflese is :an autonomic spinal cord reflexit can be inhibited or facilitated orbrain stem

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Transport of Urine from the Kidney throughthe Ureters and into the Bladder

-Urine that is expelled from the bladder hasessentially the same composition as fluid flowingout of the collecting ducts

-There are significant changes in the compositionof urine as it flows through the renal calices andureters to the bladder

-Urine from collecting ductsrenal calicespace maker activity peristaltic contractions renal pelvisureterthe bladder

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- The peristaltic contraction in the ureter are

enhanced by parasympathetic stimulation and

inhibited by sympathetic stimulation

- The ureters enter the bladder through the

detrusor muscle in the trig one region of the

bladder

- Each peristaltic wave along the ureter

increases the pressure within the ureter so

that the region passing through the bladder

wall open and allows urine to flow into thebladder

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- The condition, which some of the urine in the

bladder is propelled backward into the ureter

is called vesico ureteral reflux can lead toenlargement of the urete the pressure

renal calices + structure of renal medulla

damage to these region

- When a ureter become blocked severe pain

- The pain impulses sympathetic reflex back

to the kidneys to constrict the renal arterioles

urine output from the kidney

theureterorenal reflex important for preventing

excessive flow of fluid into the pelvis of the

kidney with a blocked ureter

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Micturition Reflex-The micturition is a single complete cycle of :

1. Progressive and rapid increase of pressure.2. A period of sustained pressure.

3. Return of the pressure to the basal

tone of the bladder.

- Completely autonomic spinal cord reflex.

- Inhibited or facilitated by center in the brain :

1. Strong facilitory an inhibitory centers inthe brain stem, located mainly in the pons.

2. Several centers located in the cerebral cortex.

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- The final control of micturition as micturation

as follows :

1. The higher centers keep the mic reflex partially

inhibited except when micturition is desired.

2. The higher centers can prevent micturition even if

the micturition reflex does occur, by continual toniccontraction of the external bladder sphincter until

convenient time presents itself.

3. When it is time to urinate, the cortical centers canfacilitate the sacral micturition centers to help

initiate a micturition reflex and at the same time

inhibit the external urinary sphincter so that

urination can occur.

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-Voluntary urination :

Contracts abdominal muscles the pressure of thebladderurine enter to the bladder neckposterior urethra under pressure stressing thebladders wall.

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Abnormalities of Micturition

Types Cause

1. The Atonic Bladder - destruction of sensory

nerve fibers

2. The Automatic Bladder - Spinal Cord Damage

above the sacral region

3. The uninhibited - Lack of inhibitory signals

Neurogenic Bladder from the Brain.

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General Characteristic

Ph : 6.0 (range : 4,58)

Specipic gravity : 1.0031.030

Osmolarity : 8551335 mOsm

Water content : 9397 percent

Volume : 1200 ml/day

Color : Clear yellow

Odor : Varies depending oncomposition.

Bacterial content: Sterile

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Diuretic and Their Mechanism of Action

- A diuretic is a substance that increases the rate of

urine volume output

- Function of the diuretic

1. Increases the rate of urine volume output

2. Increases urinary excretion of solutes

*Sodium

*Chloride

3. Used clinically act by the rate of Na

reabsorpton from the tubules

* Natriuresis

* Diuresis

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4. Reabsorption Na water reabsorptiondecreaseraises renal output of many solutes:potassium (K), magnesium, calcium.

- The clinical use especially in diseases associated with

edema and hypertensi

-Can increase urine output more than 20 fold within e

few minutes after they are administered.

-The many diuretic available for clinical use have

different mechanism of action, there for, inhibit

tubular reabsorption at different sites along the renal

nephron.

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Clases Diuretic

1. Osmotic Diuretic :

* Decrease water reabsorption by increasing

osmotic pressure of Tubular fluid.

* For example : urea, mannitol, sucrose causes a marked increase in the concentration ofosmotically active molecules or ions in the tubules.

2. Loop Diuretic

* Decrease active NaClK reabsorption in thethick Ascending loop of Henle.

* For example : Furosemid, ethacynic acid,

bumetanide

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* Raise urine output of Na, Cl, K and other

electrolytes

* Impair the ability the kidneys to either

concentrate or dilute urine.

* Urinary dilution is impaired because the

inhibition of Na and Cl reabsorption in the loop

of Henle causes more of these ions to be excreted

a long with increased water excretion.

* Urinary concentration is impaired because therenal medullary interstitial fluid concentration of

these ions and therefore renal medullary

osmolarity is reduced.

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* Multiple effect, 20 to 30 precent of the

glomerular filtrate maybe delivered into the

urine,

under acut condition, urine output to beas great as 25 times normal for at least a few

minutes.

3. Thiazide Diuretics

* Inhibit NaCl reabsorption in the Early distal

tubule.

* For example : Chlorotiazide.* Under favorable conditioncause 5 to 10

percent of the glomerular filtrate to pass into the

urine.

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4. Carbonic Anhydrase Inhibitors :

* Block NaHCO3reabsorption in the P.T.

* For example : Acetazolamide

5. Competitive Inhibitors of Aldosteron

* Decrease Na reabsorption from and K secretion

into the cortical collecting tubule.

* For example : Spironolactone.

6. Diuretics that Block Na channels in the collecting

Tubules.

* Decrease Na reabsorption

* For example : Amiloride, Triamterene.

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Kidney Desease

- Two main catagories

I. Acut renal failureII. Chronic renal failure

I. Acut renal failure : Three main cztagories

1. Pre renal acute renal failure

2. Intra renal acute renal failure

3. Post renal acute renal failure

II. Chronic Renal Failure :

- An irreversible decrease in the number of

functional Nephrons

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# Post Renal Acut Renal Failure

Caused by abnormalities of the lower urinary

tract

Some of the causes of post renal acute failure

include :

1. Bilateral obstruction of the ureters or renal

pelvises caused by large stone or blood clots

2. Bladder obstruction

3. Obstruction of the urethra

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# Physiologic Effects of Acute Renal Failure

- The major physiologic effect is :

retention in the blood

retention extracelluler fluid water

retention waste products of metabolism and

electrolys-This can lead to edema and hypertension,

hyperkalemia (to more than about 8 mEq/L),

metabolic acidosis.

-In the most severe cases of acut rrenal failure

complete anuria occurs.

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Nephrotic Syndrome-Excretion of Protein in the urine because of

increased Glomerular Permeability

-The kidney disease which develop is called

Nephrotic Syndrome

-

There is increased permeability of theglomerular membrane.

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-Such disease include :

1. Chronic glomerulonephritis

2. Amyloidosis

3. Minimal change nephrotic syndrome morefrequently in children between the age of 2

and 6 years.* As muchas 40 grams of plasma protein loss

into the urine each day

* Osmotic pressure falls from a normal valueof 28 to less than 10 mmHg largeamounts of fluid leak from the capillariesall over the body into most the tissue

severe edema.

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Effects of Renal Failure on the Body Fluids

-Depends on :

1. The water and foot intake.2. The degree of impairment of renal function

-Important effect include :

1. Generalize edemawater and salt retention2. Acidosis

3. High concentration of the non proteinnitrogens especially : urea, creatinine, uric

acid.4. High concentrations of other substances

excreted by the kidney including : phenols,sulfases, phosphates, potassium, and quanidine bases.

The total conditions is called Uremia

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-The total conditions is called Uremia.

-Increase in urea and other non protein NitrogensUremia (Azotemia)

-Another effects is :

1. Anemia of erythroporetin secretion

2. Osteomalacia production of active vit. Dand phosphat retentions

3. Hypertension : caused by

a.Increased renal vascular resistance

b.Decreased glomerular capillary filtration coefficient.

c.Excessive tubular sodium reabsorption.

d.Patchy renal damage and increased renal secretion of renin.

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Treatment of Renal Failure by Dialysis with an Artificial Kidney

-Indication : * aentely renal failure (severe)

* clironically (ESRF)

-The basic principles of the artificial kidney is to pass blood

through minute blood channels bounded by a thin membrane

there is a dialyzing fluid into which unwanted substances inthe blood pass by diffusion

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-In normal operation of the artificial kidney, blood flows

continue or intermittently back into the vein

-The rate of move ment of solute a cross the D. membrane

depends on

1. The concentration gradient of the solute betweenthe two solutions

2. The permeability of the membrane to the solute

3. The surface area of the membrane, and4. The length of time that the blood and fluid remain

in content with the membrane

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-To prevent coagulation of the blood in the artificial kidney,

a small amount of heparin is infused into the blood as it

enters the artificial kidney

-The effectiveness of the artificial kidney can be expressed in

terms of the amount of plasma that is cleared of different

substances each minute

-Most artificial kidneys can clear urea from the plasma at a

rate of 100225 ml/min, which shows that least for the

excretion of urea

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-The artificial kidneys can function about twice as rapidly as

two kidneys together, whose urea clearance is only 70 ml/min

-Yet the artificial kidneys is used for only 4 to 6 hours per day,

three time a weakthe overall plasma clearance is stillconsiderably limited when the artificial kidney replace the

normal kidneys

Thus : that the artificial kidney cannot replace some of the other

functions of the kidneys, such as secretion of

erythropoietin, which to necessary for red blood cell

production.