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the vasa recta, so bloodis isotonic as it entersand leaves the medullaThis countercurrentexchange preventsdissolution of themedullary osmotic gradient whileproviding blood to the renal medulla Potential ramifications of renal failureUremic toxicity – retention of waste productsNausea, vomiting, diarrhea, ulcers caused by toxic effect ondigestive systemBleeding tendency arising from toxic effect on platelet functionMental changes – reduced alertness, insomnia, shorterned attention span, progressing to convulsions and coma – caused by toxic effects on CNSAbdormal sensory and motor activity caused by toxic effect on peripheral nerves
Metabolic acidosis – caused by inability of kidneys to adequately secrete H+ that is continually beingadded to the body fluids as a result of metabolic activity (among most life-threatening consequences of renal failure)Altered enzyme activity caused by action of too much acid on enzymesDepression of CNS – too much acid interfering with neuronal excitabilityPotassium retention – inadequate tubular secretion of K+ (among most life-threatening consequence of renal failure)Altered cardiac and neural excitability as a result of changing the resting membrane potential of excitable cellsSodium imbalances – inability of kidneys to adjust Na+ excretion to balance changes in Na+consumptionElevated bp, generalized edema, congestive heart failure if too much Na+ is consumedHypotension and circulatory shock if too little Na+ consumedPhosphate and calcium imbalances – impaired reabsorption of electrolytesDisturbances in skeletal structures caused by abnormalities in deposition of calcium phosphate crystals (harden bone)Loss of plasma proteins – increased “leakiness” of glomerular membraneEdema caused by reduction in plasma-colloid osmotic pressureInability to vary urine concentration – impairment of countercurrent systemHypotonicity of body fluids if too much H2O is ingestedHypertonicity of body fluids if too little H2O is ingestedHypertension – combined effects of salt and fluidretention and vasoconstrictor action of excessangiotensin IIAnemia – inadequate erythropoietin productionDepression of immune system – toxic levels of wastesandacids; increased susceptibility to infectionsMicturition (urination)Urine is temporarily stored in the bladder and emptiedby micturition; moves from ureters to the urinary bladderby peristalsis
The bladder can accommodate up to 250-400 mL of urine before stretch receptors initiate the micturition reflex