Bladder & Micturition

Question 1

Flow of urine in men vs. women

Answer 1

• men: kidney => ureter => bladder => prostate => urethra
• women: kideny => ureter => bladder => urethra

Question 2

Female urethral structures responsible for continence

Answer 2

• intrinsic sphincter = bladder neck muscle fibers + mid-urethral complex

Question 3

Male urethral structures responsible for continence

Answer 3

• instrinsic sphincter = bladder neck circular muscle fibers +
• smooth muscle of prostate & membarnous urethra

Question 4

Parasympathetic and Sympathetic lower urinary tract innervation

Answer 4

• parasympathetic
  
  • innervate detrusor muscle
  • activation ==> detrusor muscle contraction and micturition
• sympathetic
  
  • inhibits detrusor contraction
  • increases tension in the smooth muscle of the bladder neck/proximal urethra
  • prevents micturition until parasympathetic stimulation

Question 5

Motor (somatic) innervation of lower urinary tract

Answer 5

• bladder, pelvic floor, and urethral sphincter arises from segments S2-S4
• sensations of bladder fullness or stretch are conveyed through long neurons form the spinal cord to the pons

Question 6

Major CNS sources of lower urinary tract innervation

Answer 6

• TSH = T10-L2 (thoracolumbar) ==> sympathetic ==> hypogastric
• SPP = S2-S4 (sacral) ==> Parasympathetic ==> Pelvic nerves
• SMP = S2-S4 (sacral) ==> Motor (somatic) ==> Pudendal nerves
• Voluntary control =
  
  • brain stem + cerebellum ==> facilitatory
  • cerebral cortex = predominatly inhibitory

Question 7

Micturition cycle

Answer 7

1 Increase in wall tension in the bladder

2 Afferent input overcomes the pontine micturition center threshold and provides cortical egress micturition begins

3 Pudendal nerve activity ceases, the external sphincter/pelvic floor relaxes, detrusor neurons are freed and discharge

4 Proximal urethra opens

5 Bladder immediately contracts

Question 8

Urinary reflex summary

Answer 8

Question 9

Major types of incontinence

Answer 9

• stress incontinence
• urge incontinence
• overflow incontinence

Question 10

Characteristics of stress urinary incontinence

Answer 10

• involuntary, sudden loss of urine during increases in intra-abdominal pressure
  
  • e.g. laughing, sneezing or coughing
  • exercising or routine activity

Question 11

SUI in women vs. men

Answer 11

• women
  
  • pelvic muscle strain
  • childbirth
  • pelvic muscle tone loss
  • estrogen loss/menopause
• men
  
  • fail to effectively control pelvic floor muscles

Question 12

Common causes of male lower urinary tract obstruction

Answer 12

• bladder neck/prostate
  
  • BPH**
  • prostate or bladder cancer
  • stricture following surgery, trauma, XRT (radiotherapy)
• urethra
  
  • stricture**
  • urethral cancer
  • diverticulum