structure and function of the lower urinary tract part 1 W2 Flashcards
what structures does the lower urinary tract include
bladder, urethra
what does the urethra have protection from
fascia, pubic ramus (anterior), iliac wings (posterior)
where does the peritoneum lie in relationship to the bladder
superiorly
what forms the borders of the trigone
ureteral openings/orifices
internal urethral meatus
layers of the bladder?
transitional epithelium / urothelium
lamina propria
difference in the detrusor muscle between sexes? why?
male detrusor thicker as works against resistance from prostate gland
bladder apical membrane features
important role in cellular signalling
signals sent via tight junctions
papillary bladder tumour symptoms?
painless visible haematuria
bladder discomfort
urgency and frequency to pass urine
layers of the bladder wall?
urothelium
lamina propria
detrusor muscle and stroma
adventitia/serosa
urothelium features
multi-layered epithelium
apical (umbrella cells)
functions - barrier, afferent signalling
lamina propria features
functional centre coordinating urothelium and detrusor
contains blood vessels, nerve fibres and myofibroblasts
detrusor muscle and stroma features
smooth muscle arranged in bundles
functional syncytium
each detrusor cell 600x5 microns
stroma - collagen and elastin
innervation of muscle = postganglionic parasympathetic system
normal bladder functions?
compliant reservoir for urine storage
barrier function
volitional voiding (muscular function)
barrier function of bladder?
GAG layer, tight junctions
passive passage of urea, Na, K
resists water passage but not truly waterproof
damage to urothelium - role in disease
how does the bladder store urine at a low pressure
highly compliant (dependant on visco-elastic properties of the bladder and relaxation of the detrusor)
neurology of bladder
bladder filling sensors detect increase in wall tension
afferent neurons to dorsal horn of sacral spinal cord
sensory/real time data on bladder state relayed to brainstem and higher centres
volitional (voluntary) micturition/voiding?
spino-bulbar reflex
modulation by pontine micturition centre (barringtons nucleus)
onufs nucleus in intermediolateral S2,3,4
when does the bladder feel full/uncomfortable?
fullness at 250ml
uncomfortable at 500ml (can lead to involuntary detrusor contractions)
what occurs during voiding
detrusor contraction
urethral relaxation
relaxation of external urethral sphincter
urine enters posterior urethra
what areas of the brain are involved in micturition? (urinating)
prefrontal, hypothalamic, thalamic, cerebellar areas and pons (most importantly)
neurotransmitters involved in bladder function?
acetylcholine - excitatory
role for nitric oxide in relaxation of bladder neck/EUS
GABA and glycine - inhibitory
facilitation and inhibition
facilitation - contraction of detrusor and relaxation of sphincter when bladder is less than full (eg anxious states)
inhibition - postponement of voiding
what happens when control of voiding from higher centres is lost?
control by spinobulbar reflexes
typically reflex voiding (not socially convenient)
can be caused by spinal cord injuries
spinal cord lesions leading to different clinical features for voiding?
suprapontine lesion
spinal (infrapontine-suprasacral) lesion
sacral/infrasacral lesion
suprapontine lesion features?
predominantly storage symptoms
insignificant PVR urine volume
detrusor overactivity
spinal (infrapontine-suprasacral) lesion features?
both storage and voiding symptoms
PVR urine volume normally raised
detrusor overactivity, detrusor-sphincter dyssynergia
sacral/infrasacral lesion features
predominantly voiding symptoms
PVR urine volume raised
hypocontractile or acontractile detrusor
PVR?
post void residual volume
seen on ultrasound
