Final answer:
Kidney and bladder functions reach adult levels by adulthood.
Step-by-step explanation:
Kidney and bladder functions reach adult levels by the time of adulthood. The kidneys play a crucial role in filtering blood and removing waste products, producing urine that is stored in the bladder before elimination through the urethra.
The process of kidney maturation occurs throughout childhood and adolescence, with kidney function reaching adult levels by adulthood.