How many sphincters are located in the bladder? What is their nerve roots?
1) Internal – present only in men. Physiological sphincter. It is relaxed during micturition via the S2-S4 parasympathetic nervous system.
2) External – Skeletal muscle under voluntary control.
What is the muscle of the bladder wall called? How many layers is it made up of? What arrangement do these muscles take?
Detrusor muscle Detrusor muscle made up of Inner layer of longitudinal muscle, circular muscle, and outer layer of longitudinal muscle.
Arranged randomly to confer strength to urinary bladder irrespective of direction of contraction.
What neurones control the storage phase of the bladder? What nerve do these neurones originate from? What would happen if these neurones were damaged?
• Commanded by sympathetic neurones T10 to L2. T12-L2 is hypogastric nerve.
• Fight or flight, don’t want to void bladder during this period.
• Damage of these neurones results in incontinence and inability to retain urine
What neurones control the bladder voiding phase?
Commanded by parasympathetic neurones S2-S4 (pelvic nerve)
What nerve controls the external urethral sphincter?
Somatic nervous supply via the pudendal nerve (S2-S4 also) gives us ability to control the external urethral sphincter.
What would happen if the bladder voiding phase neurones were damaged?
• Damage of these neurones results in retention and inability to expel urine.
o Can lead to overflow incontinence where the pressure of stored urine builds up until it starts to leak out or flow out.
What receptors are located in the bladder?
o Parasympathetic M3 receptor – activated by Ach
o Sympathetic Beta3 receptor – Activated by NA
What receptors are located in the urethra?
o Sympathetic alpha1 receptor – Activated by NA
What receptors are located in the external sphincter?
o Somatic nicotinic receptor – Activated by ACh
Describe a reflex bladder and how it occurs
• Damage to spinal cord above S2 results in afferent signals from bladder unable to reach brain
• Patient has no awareness of bladder and it is constantly relaxed
• PS initiates detrusor contraction in response to bladder wall stretch
• Therefore, bladder automatically empties as it fills.
Describe a flaccid bladder and how it occurs
• Damage to spinal roots S2-S4 results in detrusor muscle paralysis
• Bladder fills uncontrollably and overflow incontinence occurs.
What are the 4 types of urinary incontinence and define them?
• Stress UI – Involuntary leakage on sneezing or coughing or on effort or exertion
• Urge UI – Involuntary leakage accompanied by or immediately proceeded by urgency
• Mixed UI – Involuntary leakage associated with urgency and also with exertion, effort, sneezing, or coughing
• Overflow incontinence
How would you investigate a patient with urinary incontinence?
History, urine dipstick, cystoscopy
How would you manage a patient with urinary incontinence? How is it different for stress UI and urge UI?
Stress UI: Pelvic floor muscle training
Urge UI: Bladder training