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Module 104 - Nutrition, metabolism & excretion > T3 L12 Function of lower urinary tract > Flashcards

T3 L12 Function of lower urinary tract Flashcards

1
Q

What structures are involved in the passage of tubular fluid out of the kidneys & body via the urinary tract?

A

Ureters
Urinary bladder
Urethra

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2
Q

What processes are used to generate tubular fluid within the nephron?

A

Filtration
Reabsorption
Secretion

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3
Q

Where does the tubular fluid exit the collecting duct at?

A

At the tip of the renal pyramid (pelvis)

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4
Q

What leads to the renal pelvis?

A

Minor & major calyxes

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5
Q

Wha triggers peristaltic contractions at the hilus?

A

Distention

Pacemaker cells are activated by stretch

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6
Q

Describe the structure of the ureters

A

30cm long tubes
Mucosal layer
Supported by layers of smooth muscle
Lumen has folds in the relaxed state which dilate out when the peristaltic wave & pulse of urine pass through ureter

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7
Q

Describe the mucosal layer of the ureters

A

Transitional epithelium
3-8 cells thick
Impermeable to urine

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8
Q

What layers of smooth muscle are present in the ureter?

A

Inner: longitudinal muscles
Outer: circular/spiral muscles
Extra outer layer of longitudinal muscle

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9
Q

What is the function of the ureters?

A

Dilation of renal pelvis generates an action potential from the pacemaker cells in the hilum
Peristaltic waves are generated at 1-6 per minute

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10
Q

What modulates the rate of peristaltic contractions?

A

Parasympathetic nervous system enhances 5-6 waves per min

Sympathetic nervous system inhibits to slow waves in times of stress

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11
Q

What are peristaltic contractions?

A 
Similar to those in GI tract
1) Longitudinal muscle contracts
2) Circular muscle relaxes
3) Longitudinal muscle relaxes
4) Bolus can form
5) Circular muscle contraction
6) Pushes against bolus 
Pattern of contraction results in slow, progressive movement of a pulse of urine
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12
Q

Describe the entrance of ureters into the bladder

A

Ureters attach to posterior wall & pass through at an oblique angle for 2-3 cm into bladder
Ureter openings are slit like

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13
Q

What is the structure of the urinary bladder

A

Hollow muscular organ with funds & neck
Outer detrusor muscle layer
Inner mucosal layer
Trigone

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14
Q

What is the trigone?

A

Triangular sheet of muscle bounded by the openings of the ureters & entrance to urethra
Acts as a funnel

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15
Q

Describe the inner mucosal layer of the urinary bladder

A

Transitional epithelium
Folded into rugae when bladder is empty
Highly elastic

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16
Q

What is the function of the urinary bladder?

A

Temporary store of urine - holds up to 1L

Stimulated to contract by parasympathetic nervous system

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17
Q

What are the 2 sphincters controlling the exit of urine?

A

Internal urethral sphincter

External urethral sphincter

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18
Q

What is the internal urethral sphincter?

A 
Loop of smooth muscle
Convergence of detrusor muscle
Under involuntary control
Normal tone keeps neck of bladder &. urethra free from urine
Impacted in incontinence
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19
Q

What is the external urethral sphincter?

A

Circular band of skeletal muscle where urethra passes through urogenital diaphragm
Acts as a valve with resting muscle control
Under voluntary control
Voluntary relaxation permits micturition
Damaged in childbirth

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20
Q

Describe the urethra in females

A

Opens via external urethral orifice between clitoris & vagina
Shorter urethra - higher risk of UTIs
External sphincter is not as well developed

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21
Q

Describe the urethra in males

A

Passes through prostate gland & through urogenital diaphragm & penis
Longer urethra

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22
Q

Describe prostate gland enlargement

A

Occurs in 50% of males above 60
Occurs along with hypertrophy of detrusor muscle
May require surgical or hormonal treatment

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23
Q

What are the 2 stages in emptying the bladder?

A

1) Bladder fills until pressure within bladder reaches a threshold level
2) Elicits micturition reflex which produces a conscious desire to urinate

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24
Q

What inhibits the autonomic reflex?

A

Higher centres in the brain inhibit the micturition reflex

Prevents micturition be stimulating continual tonic contraction of external sphincter

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25
What facilitates the autonomic reflex?
Cortical centres in the brain facilitate urination by initiating micturition reflex & relaxing external sphincter. Internal sphincter relaxes at same time & urination occurs
26
When do periodic reflex contractions of a short duration occur?
Above 200ml or urine In a partially full bladder the contractions spontaneously relax after a few seconds Increasingly full bladder = contractions more frequent, intense & last longer.
27
What nerves inhibit micturition?
Hypogastric | Pudenal nerve
28
What nerves facilitate micturition?
Pelvic nerve
29
What is the guarding reflex?
Promotes continence During bladder filling there is progressive bladder distention which stimulates the pelvic nerve via activation of stretch receptors in bladder wall & internal sphincter Activation of pelvic nerve stimulates hypogastric nerve External sphincter is held closed by the pudenal nerve
30
What does stimulation of the hypogastric nerve cause?
Relaxation & reduced excitability of bladder detrusor muscle Constriction of internal sphincter
31
What is the micturition reflex?
Bladder continues to fill with urine Stretch receptors continue to stimulate pelvic nerve Periodic reflex micturition contractions are stimulated above 200ml Full bladder sensation is conveyed to thalamus --> cerebral cortex --> desire to urinate increases
32
What does stimulation of the pelvic nerve cause?
Contraction of detrusor muscle | Relaxation of internal sphincter
33
What aids micturition?
Lowering of diaphragm Contraction of abdominal muscles Opening of internal sphincter
34
What is paraplegia?
Complete severing of nerve inputs from cerebral cortex Micturition reflexes return without cortical control Periodic unannounced bladder emptying = automatic bladder
35
What happens with partial spinal cord damage with loss of inhibitory descending damage?
Frequent urination as excitatory impulse from cerebral cortex remain unopposed Uninhibited bladder
36
What happens if there is a crush injury of the dorsal roots?
Afferent nerve destruction --> micturition reflexes lost despite a complete efferent system Bladder fills to capacity & overflows dropwise leading to overflow incontinence Atonic bladder
37
Why do infants lack voluntary control of urination?
The corticospinal connections aren't established
38
What can cause control of the micturition reflex to be lost?
Stroke injury Alzheimer's disease Problems affecting cerebral cortex or hypothalamus such as a brain tumour
39
What happens in urinary retention?
Compresses urethra & restricts urine flow | Bladder fills to capacity & there are no stretch receptors in the bladder leading to overflow incontinence
40
What is incontinence?
Failure to store urine
41
What is retention?
Failure to empty bladder | Due to bladder dysfunction or a problem with outlet of urine
42
What can heighten the incontinence urge?
``` Spicy foods Caffeine / chocolate Citrus fruits Carbonated beverages Excitement or laughter ```
43
How does acetylcholine lead to urinary incontinence?
Leads to detrusor muscle contraction & involuntary sphincter relaation
44
What is the action of anticholinergics?
Inhibit bladder contractions to relax bladder | Facilitate involuntary contractions of internal bladder sphincter
45
What is an example of an anticholinergic?
Oxybutinin
46
What are the unwanted effects of anticholinergics?
``` Dry mouth Blurred vision Palpitations Drowsiness Facial flushing ```
47
What is imipramine?
Tricyclic antidepressant Used in low doses for the short-term treatment of nocturnal enuresis for children above 10. Can have side effects on withdrawal
48
What is the mechanism of anticholinergics?
Anticholinergic & direct muscle relaxant effects on bladder Inhibits re-uptake of noradrenaline & serotonin which increases their levels
49
What is duloxetine?
Tricyclic antidepressant Increases serotonin & noradrenaline levels Use for moderate to severe stress urinary incontinence
50
What is desmopressin?
ADH analogue | Useful in children for nocturnal bedwetting
51
What is mirabegron?
Selective beta 3-receptor agonist Useful for overactive bladder syndrome Works through sympathetic nervous system
52
What are some examples of tricyclic antidepressants?
Imipramine Duloxetine Desmopressin Mirabegron
53
When are purified bovine collagen implants used?
Useful for urinary incontinence | Surgical procedure
54
How can acute urinary retention be treated?
Catheterisation | Surgery
55
How can chronic urinary retention be treated?
Pharmacological intervention | Surgery
56
What is the action of alpha adrenergic blocking drugs?
Antagonist effect at alpha 1A adrenoreceptor in neck of bladder Relaxes smooth muscle at neck of bladder to increase urine flow rate
57
What cautions are indicated for alpha adrenergic blocking drugs?
Can reduce blood pressure so be careful in patients receiving antihypertensives Avoid in patients with postural hypotension
58
What are the unwanted effects of alpha adrenergic blocking drugs?
``` Hypotension Drowsiness Depression Headache Dry mouth Gi disturbances ```
59
What is the action of parasympathomimetics (choline esters)?
Agonist action at muscarininc acetylcholine receptors Increase contraction of bladder detrusor muscle Limited role in the relief of urinary retention
60
What is an example of a parasympathomimetic?
Bethanechol
61
What cautions are there for the use of parasympathomimetics?
``` Those with cardiac disorders such as arrhythmias GI ulceration asthma Hypotension Epilepsy Parkinsons Pregnancy ```
62
What are the unwanted effects of parasympathomimetics?
``` Nausea Vomiting Intestinal colic Bradycardia Blurred vision Sweating ```

Module 104 - Nutrition, metabolism & excretion (31 decks)

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