Micturition Flashcards
What is the ureter made up of?
Layers of muscle surrounded by transitional epithelium
What happens when urine enters the ureter?
Distends it and smooth muscles around it contracts
What is the frequency of peristaltic waves in the ureter?
1-6 contractions per minute
What controls the uretal peristaltic waves?
Myogenic nerves (NOT CNS)
How does the ureter open into the bladder?
Obliquely
What does the oblique opening of ureters do?
Prevents reflux of urine back into the ureters by a passive flap valve effect?
How much urine can the bladder hold without much increase in pressure?
400ml
What does the spherical structure of the bladder mean?
Pressure spreads equally all over it
What is the internal sphincter of the bladder made up of?
It’s an extension of the detrusor muscle
Is the internal sphincter under voluntary control?
No
What is the external sphincter made up of?
Two striated muscles (compressor urethrae and bulbocavernosus)
What is the external sphincter responsible for?
Continence
Is the external sphincter under voluntary control?
Yes
What length is the female urethra?
Short
What does the male urethra carry?
Urine and semen
What is urine elimination aided by in males?
Contraction of the bulbocavernosus muscles in penis
Which sex is more prone to incontinence?
Females as the external sphincter is less well developed
What is the lining of the bladder made of?
Transitional epithelium
What type of muscle is the bladder made up of?
Detrusor muscle
Does the composition of urine change in the urinary bladder?
No
What is the bladder permeable to?
Lipophilic molecules
What is the bladder impermeable to?
Salt and water
What is the technical name for kidney stones?
Renal calculi
Where can renal calculi form?
Anywhere along the urinary tract
What do kidney stones develop from?
Crystals that separate from urine within the urinary tract
What are the majority of stones made up of?
Calcium (usually as calcium oxaloate or calcium phosphate)
What are other (non calcium) renal calculi made up of?
Uric acid, struvite or cysteine
Why are kidney stones more common in men than in women?
Testosterone
What are renal calculi caused by?
- Excess dietary intake of stone forming substances
- poor urinary output/ obstruction
- altered urinary pH
- low concentration of inhibitors
- infection
What is ureterolithiasis?
When kidney stones make it into the urethra
What are the symptoms of ureterolithiasis?
Dysuria, haematuria, loin/back pain, reduced urine flow
What is renal colic?
When a urinary tract obstruction causes the pressure to reach 50 mmHg - considerable pain
What is dysuria?
Painful urination
What is strangury?
Stone approaching the tip of the urethra inhibiting micturition, causing intense pain
What is micturition controlled by?
Brain and spinal cord
Which part of the nervous system does the hypogastric nerve serve?
Sympathetic
Which part of the nervous system does the pelvic nerve serve?
Parasympathetic
Which part of the nervous system does the pudendal nerve serve?
Somatic
What does the sensory (/afferent) nerve do in the bladder?
Sensation of fullness and also pain from disease
What does the motor (/efferent) nerve do in the bladder?
Causes contraction and relaxation of detrusor muscle and external sphincter to control micturition
Which ganglia are closer to the bladder?
Parasympathetic
Do the parasympathetic and sympathetic neurons interact near the bladder?
Yes
What causes the detrusor muscle to contract (and what receptor)?
ACh (muscarinic receptor) or ATP (purinergic receptor)
What drug inhibits detrusor contraction?
Atropine
What inhibits transmission at bladder parasympathetic ganglia and what does this do to the muscle?
Noradrenaline- detrusor muscle relaxes
What do nitric oxide and ACh do to the internal sphincters and what nervous system do they work on?
Relax the internal sphincter - parasympathetic
What do noradrenaline do to the internal sphincters and what nervous system do they work on?
Contract- sympathetic
What does ACh do to the external sphincter and what nervous system do they work on?
Holds it closed - somatic
What are the two types of afferent nerve fibres in the bladder?
A and C
What do A fibres in the bladder sense?
Tension in detrusor muscle (filling of bladder or muscle contraction)
What do C fibres sense in the bladder?
Damage and inflammatory mediators
What do A fibres in the bladder cause?
Bladder fullness/ discomfort
What do C fibres in the bladder cause?
Pain (urgent need to micturate)
Where is the main afferent pathway to the bladder?
Pelvic nerve (parasympathetic)
What do the small myelinated alpha fibres in the pelvic nerve cause?
Micturition reflex
Where are the unmyelinated C fibre endings?
In/ near the epithelium
What type of sensors make up the hypogastric and pudendal pathways?
Nociceptors or flow receptors
At what urine volume do you get the first desire to micturate?
150ml
Why are the bladder sphincters closed when the bladder is empty?
Tonic activity from the sympathetic and somatic nerves
How does the detrusor muscle relax progressively?
Sympathetic activity inhibiting the parasympathetic transmission
In which groups is micturition an autonomic reflex?
Babies or adults with their spinal cord transacted above the sacral region
What higher centres are involved in modification of the micturition reflex?
Cortical and subcortical areas including specific pontine micturition centre
Which parts of the bladder can you contract consciously?
External sphincter and elevator muscle
What does urethritis do?
Cause the urine stream to be halted by strangury
What is urethritis?
Inflammation of urethra from STI or renal calculi
What can inhibit micturition in men?
Pinching the glans penis
How do you get woken up by needing the toilet at night?
If bladder is filled to capacity, its recognised by PMC and arousal centre which wakes you up
Why is it important that you completely empty your bladder?
If bacteria enters the urine, complete emptying restores the sterility
What happens if you retain non-sterile urine?
Causes a UTI
Where can UTIs happen?
Anywhere along the urinary tract
What is cystitis?
UTI in bladder
What is pyelonephritis?
UTI in kidneys
Which sex are UTIs more common in?
Women because of short urethra
When do UTIs become common in men?
Prostatic disease causes a bladder outflow obstruction
What are some risk factors for UTIs?
Diabetes mellitus, long term catheterisation, pregnancy, enlarged prostate, prolonged immobility, kidney stones, bowel incontinence
Causes of incontinence?
- Weakening of sphincters (stress incontinence)
- failure of nervous control
- overactive bladder
What is an overactive bladder?
Detrusor contracts spastically, resulting in a sustained high bladder pressure
What are the treatments available for incontinence?
- Anti-muscarinics
- bladder retraining
- surgery
- sacral nerve stimulation
- stem cell therapy
- tissue engineered bladder
How do antimuscarinics help treat incontinence?
Relax smooth muscle and decrease detrusor contraction
What types of incontinence is bladder retraining used for?
Stress and urge incontinence
How do you retrain your bladder?
Kegel exercises
What are the two surgeries used for treatment of incontinence?
Bladder neck suspension
Botulinum toxin injections into muscles around the urethra -> relaxes bladder
