Final answer:
Urine can be more or less concentrated depending on the individual's state of hydration. Urine osmolality tests indicate that properly functioning kidneys can concentrate or dilute urine to maintain homeostasis. While blood generally has a stable concentration, urine's concentration varies and can exceed blood's under certain conditions.
Step-by-step explanation:
When comparing the concentrations of urine vs. blood, it is notably that the concentration of dissolved particles can vary. Urine is formed by the kidneys filtering wastes from the blood and contains water, salts, and nitrogen-containing molecules.
Urine osmolality is a measure of the number of dissolved particles in urine and a crucial indicator of kidney functionality. Proper kidney function is reflected when urine concentration can fluctuate based on fluid intake: becomes more concentrated with less water intake and more diluted with greater water intake. The urine's concentration is typically measured using specific gravity or osmolality tests. For instance, during a concentration test, normal kidney functionality is indicated when the specific gravity reaches 1.020 after the injection of pituitrine.
The density of whole blood is about 1.060 g/mL. Meanwhile, the density of urine generally ranges from 1.0050 g/mL to 1.030 g/mL, indicating it can be more or less concentrated based on various factors such as hydration level. High specific gravity in urine may indicate dehydration, whereas low specific gravity may be a sign of renal failure. In contrast, the concentration of substances in blood plasma is generally more stable. During maximal clearance, large volumes of urine excretion can reflect plasma concentration, suggesting that urine can be more concentrated at times than blood.