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Renal > the lower urinary tract > Flashcards

the lower urinary tract Flashcards

1
Q

what does urine transport, storage and elimination involve

A
  1. passage of tubular fluid out of kidneys and body via urinary tract
    - ureters
    - urinary bladder
    - urethra
  2. control of bladder function
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2
Q

explain how urine exits the kidneys out of the end of the collecting duct

A
  1. tubular fluid generated within the nephron by processes of filtration, reabsorption and secretion
  2. final modification of tubular fluid occurs in collecting duct under influence of ADH
  3. tubular fluid travels through common collecting duct deep into inner medulla of kidney
  4. tubular fluid exists collecting duct at tip of renal pyramid (also known as renal papilla)
    - a site of drug induced nephrotoxicity
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3
Q

describe the exit of urine out of the kidneys into the renal pelvis and ureter

A
  1. minor and major calyces lead to renal pelvis
  2. fluid deposition into renal pelvis stretches smooth muscle
  3. distension triggers peristaltic contractions at hilus
  4. fluid moves down ureter in pulses towards bladder for storage and controlled release
  5. there is no further modification of tubular fluid in lower urinary tract after leaving kidney
    - the epithelium is impermeable to water and solutes
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4
Q

describe the structure of ureters

A
  1. tubes approx 30cm long
  2. mucosal layer: transitional epithelium
    - 3-8 cells thick, impermeable to urine
  3. supported by layers of smooth muscle
    - inner: longitudinal muscle
    - outer: circular/spiral muscle
    - final third: extra outer longitudinal layer
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5
Q

describe the function of ureters

A
  1. dilation of renal pelvis generates action potential from pacemaker cells in hilum
  2. peristaltic waves generated (between 1-6 per minute)
    - the number of contractions can be modulated by nervous system
    - parasympathetic= enhanced
    - sympathetic= inhibited
    - the lumen dilates out when peristaltic wave and pulse of urine pass through ureter
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6
Q

what are peristaltic contractions and how to they occur

A
  1. consist of successive waves of contractions and relaxation of longitudinal and circular smooth muscle
  2. longitudinal muscle contracts first followed by circular muscle relaxation
  3. longitudinal muscle then starts to relax allowing a bolus to form followed by circular muscle contraction which pushes against the bolus
  4. pattern of contraction is repeated resulting in slow but progressive movement of a pulse of urine along the ureter
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7
Q

describe the entrance of urine in the urinary bladder

A
  1. ureters attach to posterior wall of urinary bladder
  2. pass through bladder wall at oblique angle for 2-3cm into bladder
    - ureteral openings are slit like rather than rounded
    - together this helps prevent back flow of urine up ureters during contraction of bladder
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8
Q

describe the structure of the urinary bladder

A
  1. a hollow muscular organ, consisting of fundus (body) and neck
  2. outer detrusor muscle layer- consists of longitudinal, circular/spiral muscles
  3. inner mucosal layer- transitional epithelium, folded into rugae when bladder empty
    - highly elastic, expands as bladder fills
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9
Q

what is the trigone

A

triangular area bounded by openings of ureters and entrance to urethra
- acts as a funnel to channel urine towards neck of bladder

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10
Q

what is the function of the urinary bladder

A
  1. temporary storage of urine
    - up to 1L capacity
    - stimulated to contract by parasympathetic NS
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11
Q

describe the exit of urine in the urinary bladder

A

guarded by 2 sphincters:

  1. internal urethral sphincter- loop of smooth muscle
    - convergence of detrusor muscle
    - under involuntary control
    - normal tone keeps neck of bladder and urethra free of urine
  2. external uretheral sphincter- circular band of skeletal muscle where urethra passes through urogenital diaphragm
    - acts as a valve with resting muscle tone
    - under voluntary control
    - voluntary relaxation permits micturation
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12
Q

describe the elimination fo urine in females

A

the urethra in both sexes marks the end of the urinary tract

  1. opens via external urethral oriface located between clitoris and vagina
  2. shorter urethra in females- more susceptible to UTIs
  3. external sphincter not as well developed- incontinence following childbirth due to injury
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13
Q

describe the elimination of urine in males

A
  1. urethra passes through prostate gland and through pro-genital diaphragm and penis
  2. longer urethra compared to females provides some protection against UTIs
  3. prostate gland enlarges in 50% of males >60years
    - may require surgical or hormone treatment
    - prostate cancer
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14
Q

what are the 2 stages of emptying of the bladder

A
  1. bladder progressively fills until pressure within bladder reaches a threshold level
  2. this elicits the micturation reflex which produces a conscious desire to urinate or eventual emptying of bladder
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15
Q

describe what micturation is

A
  1. the micturation reflex is an autonomic reflex which can be inhibited and facilitated by higher and cortical centres in brain
    - higher centres keep the micturation reflex under inhibition, preventing micturation by continual tonic contraction of external sphincter
    - cortical centres facilitate micturation by initiating the micturation reflex and relaxing the external sphincter
    - internal sphincter relaxes at the same time and urination occurs
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16
Q

describe what occurs during the filling of the urinary bladder (graphically)

A
  1. bladder fills at 1ml/min at normal levels of hydration
  2. as bladder fills, intravesical pressure increases
  3. red solid line- normal intrinsic tone of bladder wall
  4. red broken lines- pressure peaks (micturation contractions or waves)
    - these are periodic reflex contractions of short duration which occur above approx 200ml urine volume
  5. partially full bladder- contractions relax spontaneously after a few seconds
  6. increasingly full bladder- contractions more frequent, intense and last longer
17
Q

how is micturation inhibited

A

inhibited by activity in the hypogastric and pudendal nerves

- it is facilitated by activity in the pelvic nerves

18
Q

what are the problems with micturation reflex

A
  1. control of micturation can be lost due to:
    - stroke injury, alzhiemers disease, problems affecting cerebral cortex or hypothalamus
  2. bladder sphincter muscles can lose tone (eg after pregnancy), leading to urinary incontinence
  3. urinary retention may develop in males if enlarged prostate gland compresses the urethra and restricts blood flow
19
Q

what is the functional classification of the micturation reflex

A
  1. failure to store urine- incontinence
  2. failure to empty bladder- retention
    - due to bladder dysfunction
    - due to problem with outlet of urine
20
Q

how can urinary incontinence occur

A
  1. loss of sensory nerves- due to injury
    - bladder fills to capacity
    - no signals from stretch receptors in bladder
    - overflow incontinence occurs
  2. involuntary bladder contractions- due to injury
    - urge incontinence or increased frequency
  3. heightened urge incontinence- sensitive bladder
    - spicy food
    - caffeine, chocolate
    - citrus fruits
    - carbonated beverages
21
Q

give examples of drugs used in urinary incontinence

A
  1. anticholinergics (muscarinic ACh receptor antagonists)
    - eg. oxybutinin, flavoxate
  2. tricyclic antidepressants
    - eg. imipramine
  3. duloxetine- also increases serotonin and noradrenaline levels
    - for moderate to severe stress urinary incontinence
  4. mirabegron- selective B2 receptor agonist
22
Q

describe the mechanism of action of anticholinergics in urinary incontinence

A
  • inhibit bladder contractions

- facilitates involuntary contraction of internal bladder sphincter

23
Q

describe the mechanism of action of tricyclic antidepressants in urinary incontinence

A

anticholinergic and direct muscle relaxant effects on the bladder but also inhibits reuptake of noradrenaline and seratonin, increasing their levels

24
Q

how is incontinence treated

A

Ach released onto tissue and causes detrusor muscle contraction and involuntary sphincter relaxation which causes incontinence
- We can treat incontinence by blocking Ach

25
Q

what are the unwanted effects of anticholinergics

A

dry mouth, blurred vision, palpitations, drowsiness, facial flushing

26
Q

what does acute urinary retention involve

A
  • catheterisation

- surgery

27
Q

what does chronic urinary retention involve

A
  • pharmacological intervention

- surgery

28
Q

give examples of drugs used in urinary retention

A
  1. alpha adrenergic blocking drugs
    - alfuzosin, doxazosin
  2. parasympthaomimetics- bethanecol
  3. neostigmine- inhibit breakdown of ACH and promotes incontinence
  4. finasteride- inhibitors of androgen synthesis
29
Q

describe the action of a-adrenergic blocking drugs in urinary retention

A
  • for acute and chronic urinary retention
  • antagonist action at a-adrenoceptors in bladder neck
  • relaxes smooth muscle at bladder neck and increases urine flow rate
30
Q

what are the unwanted effects of a adrenergic blocking drugs

A
  • hypotension, drowsiness, depression, headache, dry mouth, GI disturbances
  • caution: can reduce blood pressure so careful dosing required in patients receiving antihypertensive treatments
31
Q

describe the mechanism of action of parasympathomimetics

A
  • agonist action at muscarinic ACH receptors
  • increases contraction of the bladder detrusor muscle
  • limited role in relief of urinary retention
32
Q

what are the unwanted effects of parasympathomimetics

A
  • nausea, vomiting, intestinal colic, bradycardia, blurred vision, sweating
  • caution in patients with cardiac disorders, GI ulceration, asthma, hypotension, epilepsy, pregnancy

Renal (12 decks)

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