Urine Storage and Micturition Flashcards
Define renal pelvis.
The funnel-shaped dilation of the upper ureter into which urine flows from each of the renal calyces.
Where along the urinary tract can peristaltic waves be initiated?
From the renal pelvis downwards to the bladder.
Define nephrolithiasis.
The process of kidney stone formation.
List 2 treatments for nephrolithiasis.
1 - Percutaneous nephrostomy.
2 - Extracorporeal shock wave lithotripsy.
What is the average range of bladder volume?
- When empty, it is <100ml.
- When full, it can reach 1L.
List the components of the lower urinary tract.
1 - Bladder.
2 - Urethra.
3 - Prostate.
List the components of the wall of the lower urinary tract from superficial to deep.
1 - Urothelium.
2 - Lamina propria.
3 - Detrusor smooth muscle.
4 - Serosa.
What structure in the urothelium reduces permeability to substances passing through the lower urinary tract?
Tight junctions.
Where are umbrella cells located?
On the urine-facing surface of the urothelium.
List the components of the lamina propria of the lower urinary tract.
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.
What is the function of interstitial cells?
They mediate signalling between the urothelium and the detrusor smooth muscle without involving nerves.
How are the muscle cells of the detrusor smooth muscle arranged?
How is smooth muscle usually arranged?
- 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.
What type of autonomic innervation is predominant in the detrusor smooth muscle?
Parasympathetic innervation (although there is also sympathetic innervation).
Which receptors does the autonomic nervous system target in the detrusor smooth muscle?
- M3 muscarinic receptors mediate the parasympathetic effects.
- Beta 3 adrenoceptors mediate the sympathetic effects.
What are the effects of sympathetic and parasympathetic activity in the detrusor smooth muscle?
- Sympathetic activity causes relaxation.
- Parasympathetic activity causes contraction.
List the components of the continence and voiding systems.
1 - Sensory mechanisms to inform about filling.
2 - Higher control centres for voluntary voiding.
3 - Reflex pathways to generate voiding.
4 - Effectors (muscles).
List the muscle layers of the urethra from superficial to deep.
1 - Longitudinal smooth muscle.
2 - Circular smooth muscle.
3 - Striated smooth muscle.
What are the contributions of the somatic system, sympathetic system and parasympathetic system to continence?
- 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.
What are the contributions of the somatic system, sympathetic system and parasympathetic system to voiding?
- 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.
Describe the urine storage reflex.
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.
Describe the voiding reflex.
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.
List 6 instances in which urinary continence can be compromised.
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.
What is stress incontinence?
Incontinence caused by abdominal pressure exerted on the bladder.
List 7 drug treatments of overactive bladder syndrome.
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.
What is the disadvantage of using antimuscarinic drugs to treat overactive bladder syndrome?
In the long term, tolerance often occurs.
List 2 disadvantages of using botulinum toxin to treat overactive bladder syndrome.
1 - It is difficult to use.
2 - It requires ongoing treatment.
What is the target of resiniferatoxin and capsaicin when used to treat overactive bladder syndrome?
They target the sensory nerves involved in continence.
List 3 treatments for urinary outflow obstructions due to prostatomegaly.
1 - Transurethral resection of the prostate.
2 - Alpha adrenoceptor antagonists such as terazosin and tamsulosin.
3 - 5-alpha-reductase inhibitors such as finasteride.
What is the mechanism of action for alpha adrenoceptor antagonists when used to treat a urinary outflow obstruction due to prostatomegaly?
They cause relaxation of the smooth muscle of the prostate.
What is the mechanism of action for 5-alpha-reductase inhibitors when used to treat a urinary outflow obstruction due to prostatomegaly?
They reduce hypertrophy of the prostate.
