Urinary Bladder, Micturition + Infections Flashcards
Where is the bladder situated?
Pelvic cavity
BUT expands superiorly into abdominal cavity
What are the 4 parts of the bladder?
Apex
Base
Superior surface
Inferolateral surfaces
What is the trigone?
Smooth triangular area between the openings of the ureters + urethra on the inside of the bladder
What does the sympathetic nerve do?
PART 1
Transmits impulses from the pain receptors to the upper lumbar segment
= perception of pain from urethra + bladder
What does the pelvic nerve do?
PART 2
Transmit impulses from tension + pain receptors in wall of bladder
To sacral region of spinal cord
= reflex micturition + sensation of bladder fullness
What does the pudendal nerve do?
PART 3
Transmit impulses for the sensation of …
Distension of urethra
Passage of urine through urethra
Maintains tonic contractions of skeletal muscle fibres of external sphincter
Describe the sympathetic supply to the bladder
Preganglionic fibres from upper 4 L
Fibres on both sides unite to form presacral nerve
Which divide into postganglionic nerves
What are the functions of the sympathetic nerves?
Inhibitory to bladder wall (detrusor muscle)
Motor to internal urethra sphincter
Motor to seminal vesicle, ejaculatory duct + prostatic musculature
What is the muscle in the bladder wall called?
Detrusor muscle
What is found the detrusor wall?
Beta receptors (2+3)
What is found in the internal urethral sphincter?
Alpha-1 receptors
Describe the parasympathetic supply to the bladder
Preganglionic fibres arise from 2nd, 3rd + 4th sacral segments
Form pelvic nerve
Which relays in terminal ganglia in wall of urinary bladder
What are the functions of the parasympathetic nerves?
Motor to bladder wall (detrusor muscle- M3)
Inhibitory to internal urethral sphincter = urine will be released
Describe the somatic supply to the bladder
Arises from 2nd, 3rd + 4th sacral segments
Supplies the external urethra sphincter
What is the function of somatic supply?
Motor to external urethral sphincter
What is the external urethral sphincter?
Nicotinic receptors
How does the urethra empty on females?
By gravity
How does the urethra empty in males?
By several contractions of bulbocavernous muscle
What happens in the brain in micturition?
Central coordination occurs in pontine micturition centre
Parietal lobes + thalamus receive + coordinate detrusor afferent stimuli
Whilst frontal lobes + basal ganglia provide modulation with inhibitory signals
What happens when bladder is empty?
Hypogastric nerve activated (sympathetic)
= inhibitor detrusor muscle from contracting
Pelvic nerve quiet (parasympathetic)
Pudendal nerve activated (somatic)
= external urethral sphincter closed
What happens when the bladder is full?
Potine micturition centre activated
Hypogastric nerve deactivated
= contraction of detrusor muscle
Pelvic nerve activates bladder
= contracts
Pudendal nerve deactivated
= external urethral sphincter relaxes
= wee
What happens if the condition is favourable?
Cortical centre facilitates micturition by discharging signals =
Stimulation of sacral micturition centre
Inhibition of pudendal nerve
= relaxation of external urethral sphincter
Contraction of anterior abdominal muscle + diaphragm
= increase intra-abdominal pressure
= intra-vesicle pressure increased
Voiding under parasympathetic regulation
What happens if the condition is unfavourable?
Inhibit micturition reflex by =
Inhibition of sacral micturition centre
Stimulation of pudendal nerves
= contraction of external urethral sphincter
Holding of urine under sympathetic regulation
What is a cystometrogram?
Plot of intravesical pressure against volume
What changes with age?
Detrusor overactivity increases
Postpone voiding decreases
Detrusor contractility decreases
What is an atonic/hypotonic bladder due to?
Destruction of sensory nerve fibres from bladder
What happens to a atonic/hypotonic bladder?
Bladder muscle loses tone + becomes flaccid
Bladder fills to capacity + overflows = overflow dribbling
What is the treatment for atonic/hypotonic bladder?
Bladder catheterisation + correction of underlying causes
What is an automatic bladder due to?
During spinal shock after complete transection of spinal cord
How is automatic bladder treated?
After spinal shock has passed (2-6 weeks), voiding reflex returns
What is uninhibited neurogenic bladder due to?
Lesions in some parts of brain stem
= continuous excitation of spinal micturition
What happens in uninhibited neurogenic bladder?
Uncontrollable micturition
What is nocturnal micturition (bed wetting) due to?
Incomplete myelination of motor nerve fibres
= loss of voluntary control of micturition
What is overactive bladder due to?
Detrusor instability
Stroke, spinal injury + MS
Medications
What is urethral sphincter incompetence?
Dribbling with incomplete bladder emptying
What is urethral sphincter incompetence due to?
Impaired detrusor contractility + bladder outlet obstruction
Loss of collagenous support in pelvic floor = women
What is painful bladder/interstitial cystitis due to?
Urothelial abnormalities
Central sensitisation + increased activation of bladder sensory neurons
Increase in visceral sensitivity
