Micturition

Question 1

How often do peristaltic waves occur in the ureter and what is the effect?

Answer 1

Occurs at frequency of approx 1-6 contractions/minute

Ureters squeeze urine to pressure of 10-20mmHg

Question 2

Why do the ureters open obliquely into the bladder?

Answer 2

Prevents reflux of urine back into ureters by passive flap-valve effect

Question 3

What volume can the bladder hold up to w/out much increase in pressure? What structural feature causes this?

Answer 3

400ml

Spherical structure evens out pressure as it fills

Question 4

Female/Male bladder/urethra comparison

Answer 4

Female:
- Short urethra
-External sphincter poorly developed
-More prone to incontinence esp after childbirth

Male:
- Caries urine+semen
-Urine elimination aided by contraction of bulbocavernosus muscles

Question 4

What muscle is the internal sphincter controlled by?

Answer 4

Detrusor muscle ( involuntary control )

Question 5

What muscle is the external sphincter controlled by?

Answer 5

Two striated muscles
(compressor urethrae/bulbocavernosus)
Muscles responsible for continence
(voluntary control)

Question 6

Bladder lining?

Answer 6

Transitional epithelium

Question 7

Is the bladder impermeable to salt or water?

Answer 7

yes

Question 8

Is the bladder permeable to lipophlipophillic molecules?

Answer 8

Yes

Question 9

What are kidney stones?

Answer 9

• Renal calculi
• Develop from crystals that precipitate from urine
  -Calcium is present in nearly all stones (80%)
• Others made of uric acid/struvite/cysteine

Question 10

How does normal urine prevent kidney stones?

Answer 10

Contains inhibitors (citrate)

Question 11

Why are kidney stones more common in men that women?

Answer 11

Due to testosterone

Question 12

Causes of kidney stones?

Answer 12

• Excess dietary intake of stone forming substances
• Poor urine output/obstruction
• Altered urinary pH
• Low conc of inhibitors
• Infection

Question 13

What is ureterolithiasis?

Answer 13

Kidney stone disease

Question 14

Symptoms of KDS:

Answer 14

• Dysuria
• Haematuria
• Reduced urine flow
• Urinary tract obstruction

Question 15

Where can kidney stones form?

Answer 15

Kidney/ureter/bladder
anywhere in the urinary tract

Question 16

What is strangury?

Answer 16

intense urethral pain - can inhibit micturition
* can be caused by kidney stone that reaches top of the urethra
* can be caused by urethritis

Question 17

Which three nerves are involved in bladder function?

Answer 17

• Hypogastric nerve
• Pelvic nerve
• Pudendal nerve

Question 18

Hypogastric nerve?

Answer 18

Stems from T11, T12, L1, L2
Attatches to stretch receptors
Monitors fullness of bladder

Question 19

Pelvic nerve?

Answer 19

Stems from S2-S4
Attatches to stretch receptors
Monitors fullness of bladder

Question 19

Pudendal nerve?

Answer 19

Stems from S2-S4
Afferent attatches to flow receptors
Detects flow of urine

Question 20

What nervous system to each of the nerves belong to?

Answer 20

Hypogastric = sympathetic
Pelvic = parasympathetic
Pudendal nerve = somatic

Question 20

NO and ACh cause what?

Answer 20

Relaxation of internal sphincter

Question 20

Parasympathetic neurons (Efferent)

Answer 20

• Contract detrusor via ACh (muscarinic R) & ATP (purigenic R)
• Relax internal sphincter via NO (cGMP) & ACh (nicotinic R?)

ENCOURAGES MICTURITION

Question 21

Noreadrenaline causes what?

Answer 21

Contraction of internal sphincter

Question 21

How is the external sphincter kept closed?

Answer 21

Tonic activity of ACh

Question 21

Efferent nerves connect to ?

Answer 21

Muscles!

Question 22

Sympathetic neurons (Efferent)

Answer 22

* Relax detrusor * indirectly via NA (α-R) * Directly via NA (β-R) * Contract internal sphincter via NA (α-R) Inhibits micturition

Question 23

Somatic neurons (Efferent)

Answer 23

Contract external sphincter via ACh (nicotinic R) Inhibits micturition

Question 24

What are the types of afferent (sensory) nerve fibres?

Answer 24

“A fibres”: sense tension in detrusor: *Filling of bladder *Detrusor contraction *bladder fullness, discomfort “C fibres”: respond to damage & inflammatory mediators * PAIN (urgent desire to micturate)

Question 25

What causes UTIs?

Answer 25

bacteria im retained urine seeds fresh urine (urine is normally sterile) retained urine-> clinical infection

Question 26

Name of UTIs depending on location:

Answer 26

*Bladder -- cystitis or a bladder infection * Kidneys -- pyelonephritis * Ureters -- rarely the site of infection * Urethra -- urethritis

Question 27

UTI risk factors?

Answer 27

Diabetes mellitus; long-term catheterisation; pregnancy; enlarged prostate; prolonged immobility; kidney stones; bowel incontinence; advanced age

Question 28

How does BPH (benign prostatic hyperplasia) increase risk of UTI?

Answer 28

Slow urine stream → incomplete emptying → infection

Question 29

Treatments for incontinence?

Answer 29

Anti-muscarinics  relax smooth muscle & ↓ detrusor contraction Bladder retraining (used for stress & urge incontinence) (KEGEL exercises:) Surgery

Question 30

Explain the process of micturition

Answer 30

Initially – bladder empty * Sphincters closed * (tonic activity sympathetic & somatic nerves) * Bladder pressure low * Arrival of urine * Detrusor relaxes progressively * (sympathetic activity inhibiting parasympathetic transmission) * Little increase in pressure * Sphincters still closed