Control of Micturition

Question 1

Describe the structure of the Bladder wall ( Hint: 4 )

Answer 1

1- Mucosal layer : internal lining
2- submucosal layer : sensory
3- Detrusor layer ( contractile ) : smooth muscle that when stretched there is spontaneous contraction and need to urinate
4- serosa

Question 2

Explain the two phases of the bladder

Answer 2

1- Bladder filling = increased wall tension

2- Bladder emptying - micturition reflex & contraction

Question 3

Describe the anatomy of the bladder

Answer 3

Muscular sac that is flaccid when empty and turgid when full

Question 4

How does the urine enter the bladder

Answer 4

urine enters bladder from ureters via the ureteric orifices

Question 5

What stops the urine from leaving the bladder

Answer 5

2 sphincters blocking the urethra:
1 - involuntary smooth muscle sphincter - internal urethral sphincter
2- voluntary skeletal muscle sphincter - external urethral sphincter

Question 6

What structures need to contract / relax for urination

Answer 6

Both sphincters must relax and detrusor muscle must contract

Question 7

What are the interstitial cells of Cajal

Answer 7

Sensory cells that interact with smooth muscles in detrusor layer to control and initiate contraction
- Also convey sensory info to nerves

Question 8

Where are ICCs found (Hint: 3 areas )

Answer 8

Bladder, small intestine , large intestine

Question 9

What is the epithelium of the mucosal layer

Answer 9

Transitional epithelium

Question 10

What does the submucosal layer of the bladder consist of

Answer 10

1- Lamina propria with ICCs
2- nerves
3- muscularis mucosa that moves epithelium to limit urine exposure

Question 11

What does the detrusor layer of the bladder consist of

Answer 11

1- ICCs
2- smooth muscles
3- nerved

Question 12

What tones does the detrusor layer control

Answer 12

1- Basal tone for spontaneous activity

2- Expulsion tone during micturition

Question 13

Explain the afferent innervation of the bladder

Answer 13

3 bundles of sensory nerved relay info about filling bladder and sphincter pressure to spinal cord
1- Sympathetic pelvic : bladder stretch
2- Parasympathetic hypogastric : bladder stretch and internal sphincter pressure
3- Sensory somatic nerved : external sphincter pressure

Question 14

Explain the efferent innervation of bladder detrusor

Answer 14

1- Sympathetic efferent fibres from lumbar spinal cord : inhibitory
2- parasympathetic efferent from sacral spinal cord : excitatory

Question 15

Explain the innervation of the internal urethral sphincter

Answer 15

Innervated by sympathetic efferents from lumbar spinal cord

Question 16

Release of what substance contracts the internal urethral sphincter

Answer 16

noradrenaline

Question 17

Explain the innervation of the external urethral sphincter

Answer 17

Innervated by somatic efferent fibres in Pudenal nerves. Signals from brain constrict this sphincter at all times except when voiding

Question 18

What substance stimulates the skeletal muscle contraction of the external urethral sphincter

Answer 18

ACH

Question 19

Where do the somatic nerved innervating the bladder enter and emerge from

Answer 19

Spinal cord between S2&S4

Question 20

Where do the pelvic nerves innervating the bladder enter and emerge from

Answer 20

Spinal cord between S2&S4

Question 21

Where do the sympathetic nerves innervating the bladder enter and emerge

Answer 21

Spinal cord around T11-T12

Question 22

What is the micturition reflex

Answer 22

Bladder contraction reflex when the bladder fills

Question 23

Explain in detail the mechanism of the micturition reflex ( Hint: 4 steps )

Answer 23

1- Bladder fills and ICCs detect stretch
2- Parasympathetic afferent nerves synapse onto parasympathetic efferent nerves resulting in reflex arc
3- Detrusor muscle contraction is stimulated
4- voiding

Question 24

How does the bladder relax after micturition reflex without voiding and what does this allow

Answer 24

1- Pressure on the internal sphincter will stimulate a sympathetic reflex that contracts the internal sphincter and relaxes the bladder.
2- parasympathetic efferent synapse on ascending nerves to pons which results in conscious control of micturition and activates somatic efferents to close external urethral sphincter

Allows bladder to fill

Question 25

Explain in detail the mechanism of voiding (Hint: 5 steps )

Answer 25

1- Parasympathetic sensory nerved report to pons that bladder is almost full 2- parasympathetic motor nerves inhibition by pons is stopped = bladder can contract in response to stretch ( micturition reflex) 3- sympathetic motor nerves are inhibited by pons = internal sphincter relaxes 4- somatic motor signals are inhibited by pons = external sphincter relaxes 5- Voiding activated via micturition reflex causing detrusor contraction

Question 26

What are the 4 phases of micturition

Answer 26

1- after micturition signals sent to contract sphincters and relax bladder , sensory and parasympathetic inactive 2- First sensation to void : stretch detected by ICCs is communicated by nerves , parasympathetic is inhibited, sphincters still contracted 3- Desire to void: sensory neurons very active and parasympathetic inhibited, sphincters contracted 4- Voiding : parasympathetic active leading to micturition , sensory active , sphincters relaxed 5- sensory signal bladder is empty so sphincters are contracted and micturition is inactivated

Question 27

List the 4 types of incontinence ( disorders of micturition )

Answer 27

1- Stress incontinence 2- Urge incontinence 3- Overflow incontinence 4- Neurogenic incontinence

Question 28

What is Atonic bladder

Answer 28

Overflow incontinence where a large dilated urinary bladder doesn't empty

Question 29

List the causes ( in detail ) of atonic bladder

Answer 29

1- Chronic obstruction : prostate cancer, urethra narrowing 2- innervation disturbance 3- sensory nerve damage during child birth 4- adverse effect of anticholinergic medications , calcium channel blockers , adrenergic agonists 5- Epidural anaesthesia

Question 30

What is the treatment of Atonic bladder

Answer 30

1- Bethanechol ( m3 agonist ) to improve contraction force 2- catheterization 3- surgery : widen urethra, remove prostate

Question 31

What is stress incontinence

Answer 31

Bladder leakage when sneezing and coughing due to weakening of pelvic floor muscles supporting the external urethral sphincter

Question 32

List the causes of stress incontinence ( Hint: 5 )

Answer 32

1- Post-surgical complication of prostate 2- physical changes from pregnancy, child birth , menopause 3- obesity 4- caffeine 5- smoking

Question 33

What is the treatment for stress incontinence (Hint:7)

Answer 33

1- pelvic muscle exercises 2- stop mid micturition flow to improve PFM strength 3- electric stimulation of muscles 4- loose weight 5- decrease fluid intake ( caffeine & carbonated ) 6- stop alcohol , smoking 7- artificial sphincter surgery or sling to support PFM surgery

Question 34

How does smoking result in stress incontinence

Answer 34

nicotine inhibits nicotinic receptors in external sphincter which would normally bind to ACH to constrict

Question 35

What is OAB

Answer 35

Overactive bladder aka urge incontinence. High micturition frequency

Question 36

Does OAB occur with loss of bladder control

Answer 36

can occur with or without loss of bladder control

Question 37

List the causes of OAB (HINT: 7)

Answer 37

``` 1- oversensitivity due to UTI 2- oversensitivity due to over stimulation of bladder detrusor 3- obesity 4- caffeine 5- constipation 6- poorly controlled diabetes 7- chronic pelvic pain ```

Question 38

What is the treatment of OAB ( hint: 5 )

Answer 38

1- reduce bladder sensitivity by drinking more water 2- decrease caffeine and citrus 3- bladder training and behavioural methods 4- Botulinum toxin to reduce ACH release = reduce contraction 5- anti- muscarinic to reduce contraction

Question 39

List the causes of neurogenic bladder dysfunction

Answer 39

1- Spinal cord injury 2- crush injury ( child birth ) 3- stroke 3- CNS diseases

Question 40

What is neurogenic bladder dysfunction ( Explain in detail what happens )

Answer 40

When the ascending and descending inputs are lost so there is no voluntary control of micturition. Detrusor becomes overactive since there are no inhibitory influences preventing filling. Internal sphincter may be operational depending on damage.

Question 41

What is the treatment for neurogenic bladder dysfunction

Answer 41

1- Managed micturition with intermittent catheterization 2- botox capsaicin to reduce reflex voiding 3- muscarine receptor antagonist to improve filling by reducing ACH

Question 42

What is Crede's maneuver

Answer 42

manual pressure is exerted on abdomen below the navel