LSS Urinary System
NB: the renal collecting system provides an effective barrier preventing waste from re-entering the bloodstream The renal cortex has a large blood supply (arcuate arteries supply glomerulus), which then go into capillaries into loop of Henle and finally to renal papilla o This means the renal papilla is most vulnerable to death following trauma o In acute renal failure, following blood transfusion with associated increase in bp, polyuria still occurs due to malfunctioning as papilla (as papilla involved in concentrating urine)
From the major calyx, urine is drained into a single large cavity called the renal pelvis, then out through the ureter to the urinary bladder The ureters run vertically down the posterior abdominal wall, lying across the transverse spinal processes on each side of the vertebral column Clinical correlate: sites of renal colic caused by kidney stones passing through the uterers at specific junctions: o The ureteropelvic junction (between renal pelvis + ureter) o The ureter segment near the sacroiliac joint o The ureterovesical junction (between ureter + bladder) Urine is transported along the ureter by peristalisis of smooth muscle (both circular + longitudinal muscles present) The ureters open obliquely through the bladder wall, thus acting as a valve ensuring unidirectional movement of urine o Clinical correlate: vesicoureteral reflux – the abnormal movement of urine FROM the bladder INTO the ureter/kidneys. The urine collects in the pelvis in saces, dripping back down into the bladder incomplete micturition (emptying) + infection Cross section of ureter shows urothelium with tight gap junctions + plaques preventing leakage (acts as barrier/seal) o Folded walls with many cells enable stretch to accommodate urine during peristalsis o Urothelium = 3-layered epithelium with very slow cell turnover o The large luminal cells have a highly specialised low-permeability luminal membrane, which prevents the dissipation of urine-plasma gradients.
Bladder + Urethra
Vessel with pyramidal shape when empty, more spherical shape when full Capacity of 450-550ml, which voids 120-250ml of urine at each go. o NB: the bladder should NOT contract between voids Can be subdivided into fundus (base), superior + inferolateral bladder Urine transported into bladder via ureters, acts as storage vessel which then empties urine into urethra via neck NB: a median umbilical ligament exists at the apex of the bladder, as a remnant of the umbilical cord – this may be patent 3