Transcript Document

Control of Bladder
Function
9-Apr-16
Urinary Bldder
1
Urinary System
Kidney
Ureter
Aorta
Urinary
bladder
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
2
Urinary Bladder
Urinary bladder
Orifice of
ureter
Detrusor
muscles
Ureter
Trigone of
bladder
Prostatic
urethra
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
3
Urinary Bladder
Urinary bladder
Detrusor
muscles
– Stores urine
– Periodically evacuates
completely urine
Ureter
It is made up of smooth
muscles
– Detrusor muscle
• Fibers extend in all
directions
• Spiral, longitudinal,
circular
– Fused to form syncytium
Seminal
vesicle
Prostate
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
4
Urinary Bladder
Detrusor
muscles
When contracted
can
Ureter
– Increase pressure
in bladder by 40 –
60 mm Hg
Seminal
vesicle
Prostate
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
5
Urinary Bladder
On the posterior wall
of bladder
– Small triangular area
called
• Trigone
Orifice of
ureter
Trigone of
bladder
Prostatic
urethra
Lower part of trigone
opens into posterior
urethra
The ureters enter the
bladder at the upper
ends of the trigone
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
6
Innervation
Parasympathetic
Pelvic nerve from
sacral 2,3,4
Contain both
sensory and
motor fibers
Sympathetic fibers
T11 – 12 L1,2
Inhibitory to detrusor
excitatory to sphincter
Internal
sphincter
External
sphincter
Parasympathetic
fibers S 2,3,4
Excitatory to detrusor
Inhibitory to sphincter
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
7
Innervation
Sensory fibers
Sympathetic fibers
T11 – 12 L1,2
Inhibitory to detrusor
excitatory to sphincter
Internal
sphincter
External
sphincter
Parasympathetic
fibers S 2,3,4
Excitatory to detrusor
Inhibitory to sphincter
– For pain
– Detect the degree
of stretch in
bladder wall
– Initiate reflexes
for bladder
emptying
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
8
Innervation
The motor fibers
Sympathetic fibers
T11 – 12 L1,2
Inhibitory to detrusor
excitatory to sphincter
Internal
sphincter
External
sphincter
– Excite the
detrusor muscles
– Inhibit the
internal sphincter
around the
trigone
Parasympathetic
fibers S 2,3,4
Excitatory to detrusor
Inhibitory to sphincter
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
9
Innervation
The sympathetic
nerves
Sympathetic fibers
T11 – 12 L1,2
Inhibitory to detrusor
excitatory to sphincter
Internal
sphincter
External
sphincter
– From lower thoracic
and upper lumber
segments
• T11 , 12 & L 1,2,3
Parasympathetic
fibers S 2,3,4
Excitatory to detrusor
Inhibitory to sphincter
Sympathetic activity
– Inhibit the
detrusor
– Excite the trigone
– Sphincter vesicae
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
10
Sphincter Mechanism
In both male and females
There are two sphincter elements
– Internal sphincter
• Smooth muscle at the bladder neck
– External sphincter
• Skeletal muscle
• Located at the level of membranous
urethra
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Urinary Bldder
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Sphincter Mechanism
Bladder neck sphincter
– Detrusor muscle plus
– Large amount of elastic tissue
– Muscle in this area is called internal
sphincter (sphincter vesicae)
Not a true circular sphincter
– Thickening formed by
• Interlaced and converged muscle fibres
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Urinary Bldder
12
Sphincter Mechanism
Receive both
– Parasympathetic nerves
– Sympathetic
In relaxed filling state
– Bladder neck will remain closed
– Provide continence mechanism
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Urinary Bldder
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Sphincter Mechanism
With contraction
– Detrusor muscle pull open the
bladder neck
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Urinary Bldder
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Sphincter Mechanism
Beyond the posterior urethra,
– The urethra passes through
– Urogenital diaphragm
• Contain layers of muscles
Form the external sphincter
– Made up of voluntary muscles
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Urinary Bldder
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Ureters
Ducts of
Bellini
Proximal portionof
collection system
Sympathetics
Parasympathetics
9-Apr-16
Ducts of Bellini
have circular
muscles
Proximal portion
of collecting
system
– Pacemaker
activity
– Initiate peristalsis
T10
T11
T12
S2
S3
S4
Urinary Bldder
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Ureters
Ducts of
Bellini
Proximal portionof
collection system
Wave of
peristalsis
– Stretches calices
–  Inherent pacemaker
activity
Forcing urine
into bladder
Sympathetics
Parasympathetics
9-Apr-16
Urine flowing from
collecting ducts into
renal calices
T10
T11
T12
S2
S3
S4
Initiates peristaltic
contractions
– Spread to renal pelvis
down the ureters
Urinary Bldder
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Ureters
Ducts of
Bellini
Proximal portionof
collection system
Muscle tone and
peristalsis
– Influenced by rate
of urine excretion
Wave of
peristalsis
 In diuresis
Forcing urine
into bladder
Sympathetics
Parasympathetics
9-Apr-16
–  Frequency of
peristalsis
T10
T11
T12
S2
S3
S4
Urinary Bldder
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Ureters
Ducts of
Bellini
Proximal portionof
collection system
Wave of
peristalsis
Forcing urine
into bladder
Sympathetics
Parasympathetics
9-Apr-16
T10
T11
T12
S2
S3
S4
Walls of ureters
innervated by ANS
Peristaltic
contractions in
ureters
– Enhanced by
parasympathetic
– Inhibited by
sympathetics
Urinary Bldder
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Ureters
Ducts of
Bellini
Proximal portionof
collection system
– Compress the ureters
– Prevent backward flow of
urine into ureters during
micturition
Wave of
peristalsis
Forcing urine
into bladder
Sympathetics
Parasympathetics
9-Apr-16
Normal tone of detrusor
muscles
Each peristaltic wave
T10
T11
T12
–  Intra-ureteral pressure
– Force urine to flow into
bladder
S2
S3
S4
Urinary Bldder
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Uretero-renal Reflex
Well supplied by pain fibers
When ureters become obstructed
(renal stones)
– Intense reflex constriction occurs
accompanied by severe pain
– Ureteric colic
9-Apr-16
Urinary Bldder
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Uretero-renal Reflex
The pain causes reflex
– Constriction of renal arterioles
–  Urine output from the kidney
Uretero-renal reflex
– Prevent excess flow of urine
– When ureters are blocked
9-Apr-16
Urinary Bldder
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Filling of Bladder
During the collecting
phase
– Emptying is prevented
or made difficult
• By neural activity
Sympathetics
– Inhibit detrusor
muscles
– Excite internal
sphincter
Pudendal
fibers
 Urethral
pressure
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
23
Filling of Bladder
Pudendal fibers
– Excite external
sphincter
–  Intra-urethral
pressure
• Maintain continence
Pudendal
fibers
 Urethral
pressure
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
24
Urinary Bladder
Bladder fills at a rate of 50 ml/hr
– Plasticity of smooth muscle
• Stretch (stress) relaxation
– Ensure that pressure inside the
bladder
• Increases only slightly
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Urinary Bladder
When bladder collects 150 –250
ml urine
– 1st signs of brief urge to urinate
appears
– 250 –500 ml of urine
• Evacuation phase begins
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Intravesicle pressure (cm H2O)
Cystometry
Cystometry
80
– Relationship
between
60
• Intravesicle pressure
& volume
• Governed by
Laplace’s law
40
20
• P = (2T)/R
0
0
100
200
300
400
500
Intravesicle volume (ml)
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Urinary Bldder
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Intravesicle pressure (cm H2O)
Cystometry
As urine collect in
the bladder
80
– Bladder distend
– Both T & R increase
so
60
40
• Pressure does not
increase appreciably
in the initial phases
20
0
0
100
200
300
400
500
Intravesicle volume (ml)
9-Apr-16
Urinary Bldder
– Until critical
volume is attained
28
Micturition Reflex
As bladder fill with
urine
Cortex
Impulses to
spinal cord
Brain
stem
– Stretch receptors are
stimulated
– Sensory signal relayed to
spinal cord (sacral
segment)
Stretch of muscle
during filling
Cause reflex
contraction of detrusor
muscle
 Bladder
pressure
 Urethral
pressure
– Micturition reflex
– Micturition contraction
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
29
Micturition Reflex
Cortex
Impulses to
spinal cord
Brain
stem
Stretch of muscle
during filling
When the bladder is
partially full
– Reflex can relax
spontaneously
As blood continues to fill
 Bladder
pressure
 Urethral
pressure
– Reflex becomes more
frequent
–  Strength of contraction of
detrusor muscle
–  Intra-vesicle pressure
– More stimulation of stretch
receptors
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
30
Micturition Reflex
Cortex
Impulses to
spinal cord
Brain
stem
Stretch of muscle
during filling
But once the reflex
– Has not succeeded in
emptying the bladder
– It is inhibited
– Can remain inhibited
for several hours
 Bladder
pressure
 Urethral
pressure
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
31
Micturition Reflex
Cortex
Impulses to
spinal cord
Brain
stem
But as the bladder
becomes more filled with
urine
– Reflex becomes more
powerful
Stretch of muscle
during filling
Initiate reflex inhibition
of
 Bladder
pressure
 Urethral
pressure
– External sphincter via
pudendal nerves
Causing urination to
occur
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
32
Evacuation of Urinary
Bladder
During evacuation
– Perineal muscle relax
– Voluntary sphincter around urethra
relax
– Trigone contract
• Leads to occlusion of ureteral-vesicle
junction
• Prevent reflux of urine into ureters
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Urinary Bldder
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Evacuation of Urinary
Bladder
Contraction of trigone also
– Pulls open the posterior portion of
bladder neck
• Become funnel shaped
Detrusor muscle contract
– Intra-vesicle pressure begins to rise
• This pressure is directed downwards
towards urethra
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Evacuation of Urinary
Bladder
Voiding begins
– Detrusor maintain contraction until
bladder is empty
When bladder is empty
– Detrusor relax
– Bladder neck is allowed to close
– Urethra and perineal muscles tone return
to normal
– Trigone resumes its normal tone
9-Apr-16
Urinary Bldder
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Paracentral lobule
Fibers from
paracentral lobule
descend to the
micturition center to
the pelvic and
pudendal nerve
Detrusor
muscles
An initial relaxation
of perineal muscles
is followed by
contraction of
detrusor muscle.
Bladder neck closed
when detrusor
muscle relaxes
assisted by elastic
recoil
9-Apr-16
Signals reaching
the brain, initiate
desire to hold
As the Detrusor
muscle contracts
abdominal wall
muscle and
diaphragm contract,
 abdominal
pressure.
Stretch receptors
stimulated
External vesical
sphincter relaxes.
Bladder neck opens.
Voiding occurs with
at pressure of 50 to
150 cm water.
Urinary Bldder
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Facilitation & Inhibition
Cortex
Impulses to
spinal cord
Brain
stem
Stretch of muscle
during filling
Micturition reflex
– Spinal cord
phenomenon
Can be inhibited or
facilitated by brain
centers
 Bladder
pressure
 Urethral
pressure
– Brain stem, pons
– Several centers located
in cerebral cortex
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
37
Facilitation & Inhibition
Cortex
Impulses to
spinal cord
Brain
stem
Stretch of muscle
during filling
When micturition is
desired
Higher centers
– Keep micturition reflex
partially inhibited
Higher centers can
prevent micturition
 Bladder
pressure
 Urethral
pressure
– Even if reflex does occur
• Tonic contration of
external sphincter
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
Urinary Bldder
38
Facilitation & Inhibition
Cortex
Impulses to
spinal cord
Brain
stem
Stretch of muscle
during filling
 Bladder
pressure
 Urethral
pressure
From Hansen T. Sherrief;
Texbook of Physiology CD
9-Apr-16
When it is time to urinate
Higher centers can
facilitate sacral
micturition centers
– Initiate micturition
reflex
– At the same time
inhibit external
sphincter
Urination can occur
Urinary Bldder
39