Urine Storage and Micturition Flashcards

1
Q

Define renal pelvis.

A

The funnel-shaped dilation of the upper ureter into which urine flows from each of the renal calyces.

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2
Q

Where along the urinary tract can peristaltic waves be initiated?

A

From the renal pelvis downwards to the bladder.

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3
Q

Define nephrolithiasis.

A

The process of kidney stone formation.

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4
Q

List 2 treatments for nephrolithiasis.

A

1 - Percutaneous nephrostomy.

2 - Extracorporeal shock wave lithotripsy.

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5
Q

What is the average range of bladder volume?

A
  • When empty, it is <100ml.

- When full, it can reach 1L.

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6
Q

List the components of the lower urinary tract.

A

1 - Bladder.

2 - Urethra.

3 - Prostate.

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7
Q

List the components of the wall of the lower urinary tract from superficial to deep.

A

1 - Urothelium.

2 - Lamina propria.

3 - Detrusor smooth muscle.

4 - Serosa.

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8
Q

What structure in the urothelium reduces permeability to substances passing through the lower urinary tract?

A

Tight junctions.

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9
Q

Where are umbrella cells located?

A

On the urine-facing surface of the urothelium.

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10
Q

List the components of the lamina propria of the lower urinary tract.

A

1 - Blood vessels.

2 - Lymphatics.

3 - Nerves, especially sensory nerves detecting chemical and mechanical changes in the bladder.

4 - Interstitial cells.

5 - Mesh of connective tissue.

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11
Q

What is the function of interstitial cells?

A

They mediate signalling between the urothelium and the detrusor smooth muscle without involving nerves.

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12
Q

How are the muscle cells of the detrusor smooth muscle arranged?

How is smooth muscle usually arranged?

A
  • In the detrusor smooth muscle, the cells are arranged in a basket-weave pattern.
  • In most smooth muscle, the muscle cells are arranged in longitudinal and circular layers.
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13
Q

What type of autonomic innervation is predominant in the detrusor smooth muscle?

A

Parasympathetic innervation (although there is also sympathetic innervation).

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14
Q

Which receptors does the autonomic nervous system target in the detrusor smooth muscle?

A
  • M3 muscarinic receptors mediate the parasympathetic effects.
  • Beta 3 adrenoceptors mediate the sympathetic effects.
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15
Q

What are the effects of sympathetic and parasympathetic activity in the detrusor smooth muscle?

A
  • Sympathetic activity causes relaxation.

- Parasympathetic activity causes contraction.

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16
Q

List the components of the continence and voiding systems.

A

1 - Sensory mechanisms to inform about filling.

2 - Higher control centres for voluntary voiding.

3 - Reflex pathways to generate voiding.

4 - Effectors (muscles).

17
Q

List the muscle layers of the urethra from superficial to deep.

A

1 - Longitudinal smooth muscle.

2 - Circular smooth muscle.

3 - Striated smooth muscle.

18
Q

What are the contributions of the somatic system, sympathetic system and parasympathetic system to continence?

A
  • The somatic system is active and keeps external sphincter contracted.
  • The sympathetic system is active and keeps the internal sphincter contracted and the smooth detrusor muscle relaxed.
  • The parasympathetic system is inactive.
19
Q

What are the contributions of the somatic system, sympathetic system and parasympathetic system to voiding?

A
  • The somatic system is inactive (therefore external sphincter relaxes).
  • The sympathetic system is inactive (therefore internal sphincter relaxes).
  • The parasympathetic system is active and causes contraction of the bladder.
20
Q

Describe the urine storage reflex.

A

A reflex to promote urine storage when the bladder is distended:

1 - During the storage of urine, distention of the bladder produces afferent firing of the pelvic nerve.

2 - This in turn stimulates sympathetic outflow in the hypogastric nerve at the lumbar cord to the bladder.

3 - It also stimulates sympathetic outflow in the pudendal nerve at the sacral cord to the external urethral sphincter.

  • The pontine storage centre in the brain can excite the pudendal nerve through sacral preganglionics to provide voluntary control.
21
Q

Describe the voiding reflex.

A

A reflex to promote further voiding of urine when the bladder is being emptied:

1 - During the elimination of urine, afferent firing of the pelvic nerve stimulates the pontine micturition centre in the brain.

2 - This in turn stimulates parasympathetic outflow in the hypogastric nerve at the lumbar cord to the bladder.

3 - It also stimulates parasympathetic outflow in the pudendal nerve at the sacral cord to the external urethral sphincter.

22
Q

List 6 instances in which urinary continence can be compromised.

A

1 - Urinary tract infections, where chemical stimuli increase bladder activity and increase the urge to void.

2 - Spinal cord disorders such as spinal cord injuries and multiple sclerosis.

3 - Stroke.

4 - Pelvic floor injuries, e.g. following childbirth.

5 - Detrusor overactivity, leading to overactive bladder syndrome.

6 - Atonic bladder, which may be due to autonomic neuropathy.

23
Q

What is stress incontinence?

A

Incontinence caused by abdominal pressure exerted on the bladder.

24
Q

List 7 drug treatments of overactive bladder syndrome.

A

1 - Antimuscarinic drugs such as oxybutynin.

2 - Botulinum toxin.

3 - Beta 3 adrenoceptor agonists.

4 - Resiniferatoxin.

5 - Capsaicin.

6 - Type 5 phosphodiesterase inhibitors.

7 - K+ channel activators.

25
Q

What is the disadvantage of using antimuscarinic drugs to treat overactive bladder syndrome?

A

In the long term, tolerance often occurs.

26
Q

List 2 disadvantages of using botulinum toxin to treat overactive bladder syndrome.

A

1 - It is difficult to use.

2 - It requires ongoing treatment.

27
Q

What is the target of resiniferatoxin and capsaicin when used to treat overactive bladder syndrome?

A

They target the sensory nerves involved in continence.

28
Q

List 3 treatments for urinary outflow obstructions due to prostatomegaly.

A

1 - Transurethral resection of the prostate.

2 - Alpha adrenoceptor antagonists such as terazosin and tamsulosin.

3 - 5-alpha-reductase inhibitors such as finasteride.

29
Q

What is the mechanism of action for alpha adrenoceptor antagonists when used to treat a urinary outflow obstruction due to prostatomegaly?

A

They cause relaxation of the smooth muscle of the prostate.

30
Q

What is the mechanism of action for 5-alpha-reductase inhibitors when used to treat a urinary outflow obstruction due to prostatomegaly?

A

They reduce hypertrophy of the prostate.