Urine Storage and Micturition

Question 1

Define renal pelvis.

Answer 1

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

Question 2

Where along the urinary tract can peristaltic waves be initiated?

Answer 2

From the renal pelvis downwards to the bladder.

Question 3

Define nephrolithiasis.

Answer 3

The process of kidney stone formation.

Question 4

List 2 treatments for nephrolithiasis.

Answer 4

1 - Percutaneous nephrostomy.

2 - Extracorporeal shock wave lithotripsy.

Question 5

What is the average range of bladder volume?

Answer 5

• When empty, it is <100ml.

- When full, it can reach 1L.

Question 6

List the components of the lower urinary tract.

Answer 6

1 - Bladder.

2 - Urethra.

3 - Prostate.

Question 7

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

Answer 7

1 - Urothelium.

2 - Lamina propria.

3 - Detrusor smooth muscle.

4 - Serosa.

Question 8

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

Answer 8

Tight junctions.

Question 9

Where are umbrella cells located?

Answer 9

On the urine-facing surface of the urothelium.

Question 10

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

Answer 10

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.

Question 11

What is the function of interstitial cells?

Answer 11

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

Question 12

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

How is smooth muscle usually arranged?

Answer 12

• 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.

Question 13

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

Answer 13

Parasympathetic innervation (although there is also sympathetic innervation).

Question 14

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

Answer 14

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

Question 15

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

Answer 15

• Sympathetic activity causes relaxation.

- Parasympathetic activity causes contraction.

Question 16

List the components of the continence and voiding systems.

Answer 16

1 - Sensory mechanisms to inform about filling.

2 - Higher control centres for voluntary voiding.

3 - Reflex pathways to generate voiding.

4 - Effectors (muscles).

Question 17

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

Answer 17

1 - Longitudinal smooth muscle.

2 - Circular smooth muscle.

3 - Striated smooth muscle.

Question 18

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

Answer 18

• 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.

Question 19

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

Answer 19

• 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.

Question 20

Describe the urine storage reflex.

Answer 20

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.

Question 21

Describe the voiding reflex.

Answer 21

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.

Question 22

List 6 instances in which urinary continence can be compromised.

Answer 22

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.

Question 23

What is stress incontinence?

Answer 23

Incontinence caused by abdominal pressure exerted on the bladder.

Question 24

List 7 drug treatments of overactive bladder syndrome.

Answer 24

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.

Question 25

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

Answer 25

In the long term, tolerance often occurs.

Question 26

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

Answer 26

1 - It is difficult to use.

2 - It requires ongoing treatment.

Question 27

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

Answer 27

They target the sensory nerves involved in continence.

Question 28

List 3 treatments for urinary outflow obstructions due to prostatomegaly.

Answer 28

1 - Transurethral resection of the prostate.

2 - Alpha adrenoceptor antagonists such as terazosin and tamsulosin.

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

Question 29

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

Answer 29

They cause relaxation of the smooth muscle of the prostate.

Question 30

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

Answer 30

They reduce hypertrophy of the prostate.