lower urinary tract Flashcards
what are the 3 structures that urine passes through from the kidneys?
- ureters
- urinary bladder
- urethra
how does urine exit the kidneys?
- tubular fluid generated within the nephron by filtration, reabsorption, secretion
- final modification of tubular fluid occurs in collecting duct under influence of ADH
- tubular fluid travels through common collecting duct deep into inner medulla of kidney
- tubular fluid exits collecting duct at tip of renal pyramid (renal papilla)
- fluid deposition into renal pelvis stretches smooth muscle
- distention triggers peristaltic contractions at hilus
- fluid moves down ureter in pulses towards bladder for storage and controlled release
what structures lead to renal pelvis?
minor an major calyces
what are the key characteristics of the mucosal later of the ureters?
- transitional epithelium
- 3-8 cells thick
- impermeable to urine
what are the 3 layers of smooth muscle used for support in the ureters?
- inner: longitudinal muscle
- outer: circular/spiral muscle
- extra outer layer of longitudinal muscle
what is the function of the ureter?
- dilation of renal pelvis generated action potential form pacemaker cells in hilum
- peristaltic waves generated: between 1 to 6 per minute
- the number of contractions can be modulated by nervous system (PNS = enhanced, SNS = inhibited)
how do peristaltic contractions work?
- consist of successive waves of contractions and relaxation of longitudinal and circular smooth muscle
- longitudinal muscle contracts first followed by circular muscle relaxation
- longitudinal muscle then starts to relax allowing a bolus to form followed by circular muscle contraction which pushes agains the bolus
- pattern of contractions is repeated resulting in slow but progressive movement of a push or urine along the ureter (PERISTALSIS)
how does urine enter the urinary bladder?
- the ureters pass through the bladder wall at oblique angle for 2-3cm into bladder
- ureteral opening are slit-like
- together this helps prevent back flow of urine up ureters during contraction of bladder
what is the structure of the urinary bladder?
- a hollow muscular organ, consisting of a fundus and neck
- outer muscle layer: consists of longitudinal, circular/spiral muscle
- inner mucosal layer: transitional epithelium, followed into ‘rugae’ when bladder empty, highly elastic
what is the trigone?
- triangular area bounded by openings of ureters and entrance to urethra
- acts as funnel to channel urine towards neck of bladder
what is the function of the urinary bladder?
- temporary storage of urine
- up to 1L capacity
- stimulated to contract by PNS
what are the 2 sphincters that guard the urinary bladder?
1) internal urethral sphincter
2) external urethral sphincter
what are the key characteristics of the internal urethral sphincter?
- loop of smooth muscle
- convergence of detrusor muscle
- under involuntary control
- normal tone keeps neck of bladder and urethra free of urine
what are the key characteristics of the external urethral sphincter?
- circular band of skeletal muscle where urethra passes through urogenital diaphragm
- acts as a valve with resting muscle tone
- under voluntary control
- voluntary relaxation permits micturition
what are the key characteristics of a female urethra?
- opens via external urethral orifice located between clitoris and vagina
- shorter urethra in females
- external sphincter not as well developed: incontinence following childbirth due to injury