the lower urinary tract Flashcards
what is the urinary tract
ureters
urinary bladder
urethra
how does urine exit the kidneys
final mod in cd
travels through cd deep into inner medulla
exits art top of renal pyramid - aka renal papilla
site of nephrotoxicity
how does urine leave the kidney into renal pelvis and ureter
minor and major calyces lead to renal pelvis
fluid deposition into renal pelvis, stretches smooth muscle
distension triggers peristaltic contractions at hilum
fluid moves down ureter into pulses to bladder
what is the structure of the ureters
tubes 30cm long mucosal layer - transitional epithelium (3-8 cells thick, impermeable to urine) supported by SM inner longitudinal outer circular extra outer L
what is the function of the ureter
dilation of renal pelvis generatrews action potential from pacemaker cells at hilum
peristaltic waves 1-6/min
can be mod by NS
how does peristalsis work in the ureters
peristaltic contraction consists off successive waves of contraction and relaxation of L and C muscle
L contrast followed by C
then relax L and C contract to push against bolus
slow but progressive movement
aka vermiculation
how does urine enter the bladder
ureters attach to posterior wall of bladder
pass into wall at oblique angle for 2/3cm
slit like
helps to stop back flow
structure of the bladder
hollow muscular organ, fundus and neck
other detrusor muscle layer - L and C muscle
inner mucosal layer - transitional epithelium, folded into rugue when bladder empty, highly elastic
function of the bladder
temp storage of urine
up to 1L
stimulated to contract by PNS
what is the trigone
triangular area bounded by openings of ureters and entrance to urethra
acts as a funnel to channel urine to neck of bladder
what is the internal urethral sphincter of the bladder
loop of smooth muscle
convergence of detrusor muscle
involuntary
normal tone keeps neck and urethra free of urine
what is the external urethral sphincter
circular band of skeletal muscle where urethra passes to urogenital diaphragm
acts as a valve with resting muscle tone
voluntary
how does the urinary tract end in females
urethra opens via external urethral orifice located between vagina and clitoris
shorter in females
external sphincter not as well developed - incontinence after childbirth
how does the urinary tract end in males
urethra passes through prostate gland and through urogetial diaphragm and penis
longer urethra
prostate gland enlarges (50% >60yo)
prostate cancer - commonest in older men
what is micturition
2 stage process
bladder progressively fills until pressure in bladder at threshold
elicits micturition reflex, produces a conscious desire to urinate
what controls micturition
autonomic
inhibited by higher centres in brain and facilitated by cortical centres in brain (initiate and relax external sphincter)
how does the bladder fill
1ml/min at normal levels of hydration
intravesical pressure inc
periodic reflex contractions of short duration occur above 200ml
partially full - contractions relax spont
inc full - more freq, intense and longer
desire, discomfort, urgency
bladder and sphnicter inneratiobn
L2 hypogastric nerve - symp invol control
S2,3,4 - pelvic nerve PS invol
pudenal nerve - somatic, vol
HG and Pu inhibit micturition and facilitated by pelvic
what is the guarding reflex
bladder fills up, distension, stretch receptors via pelvic nerve, HG nerve (relax and red excitability of bladder detrusor muscle, constrict int sphincter)
ext sphincter held closed by pu nerve
promote continence
what is the micturition reflex
SR cont to stim pelvic nerve (detrusor contract, relax internal sphincter)
micturition contractions
full bladder sensation to thalamus and cerebral cortex to inc desire to urinate
at ap time vol relax ext sphincter via pu nerve, micturition, lower diaphragm, contract ab muscles, open int sphincter
how can paraplegia disrupt micturition
complete severing of nerve inputs from cerebral cortex
micturition reflex return but no cortical control
periodic unannounced bladder emptying (automatic bladder)
how can partial spinal cord damage with loss of inhibitory descending signals affect micturition
freq urination as excitatory impulses from cerebral cortex remain unopposed
uninhibited bladder
how can crush injuries of the dorsal roots affect micturition
afferent nerve destruction - mic reflexes loss despite effects system
fills to capacity and overflows drowse (overflow incontinene - atonic bladder)
how do infants bladders work
lack voluntary control until corticospinal connections are established
