Physiology of Micturition by Dr.jawaria

8/9/2019 Physiology of Micturition by Dr.jawaria

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MICTURITION

Dept. ofPhysiology


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Micturition (defnition)Micturition (defnition)

It is the process by which urinary bladderIt is the process by which urinary bladder

empties itself of urine when it becomesempties itself of urine when it becomes

lled.lled.

Phases: 1- Filling phasePhases: 1- Filling phase Bladder lls progressively until theBladder lls progressively until the

tension in its walls rises above a thresholdtension in its walls rises above a threshold

level this elicits the second steplevel this elicits the second step

!- "icturition re#e$: that empties the!- "icturition re#e$: that empties the

bladder.bladder.


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Body

%rigone &onthe posteriorwall'

(ec)

*moothmuscle of the

bladder&detrusormuscle' isarranged in

spirallongitudinaland circularbundles. %hemuscle

bundles pass +$ternal urethral


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Filling o the bladder

,hen urine

collects in therenal pelvis thepressure in thepelvis increases.%his increase inthe pressureinitiates a

peristalticcontractionbeginning in thepelvis and

spreading

%he walls

ofureterscontainsmooth

musclearrangedin spirallongitudinal andcircular


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!

"

#

$%mpathetic ner&esuppl%

$%mpathetic

chain

'%pogastric

ganglion

'%pogastric

ner&e Urethra

xternal

aras%mpathetic ner&esuppl% $"

$#

$*

$"$#$*

el&ic ner&e

udendal ner&e

+nner&ation o the+nner&ation o the

bladderbladder

*omaticnerve

supply


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$%mpathetic ner&e suppl%and Internal urethralsphincter apparently play no role in micturition.2owever sympathetics are nerves of lling.

aras%mpathetic ner&e suppl%

*ensory bers in the pelvic nerve carry impulses fromstretch receptors present on the wall of the urinary

bladder to the spinal centre of micturition. *timulationof parasympathetic e0erent bers causes contractionof detrusor muscle leading to emptying of urinarybladder.

$omatic ner&e suppl%

%his maintains the tonic contractions of the s)eletal

muscle bers of the e$ternal sphincter so that thiss hincter is contracted alwa s. 3urin micturition this


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%he relationship between the volume of urine andpressure in the urinary bladder &intravesical pressure'can be studied by inserting a double lumen catheter

and emptying the bladder. %hen the pressure isrecorded by connecting one lumen of the catheter to asuitable recording instrument while introducing wateror air through the other lumen. %he graphicalrecording of the pressure changes in the urinary

bladder in relation to rise in the volume of urinecollected in it is called c%stometrogram. 6ystometryis the techniue used to demonstrate this relationship.


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,%stometrogram

177 !77 877

977

Intravesicalpressure

&cm of

,ater'

;

7

Physiology of Micturition by Dr.jawaria

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