Final answer:
The kidneys remove excess substances from the blood and eliminate them in urine, playing a vital role in the urinary system which also includes ureters, bladder, and the urethra.
Step-by-step explanation:
Substances in blood in excess of the storage capacity or need of the body, such as water and ions, are removed from blood by the kidneys and eliminated in urine. The urinary system plays a crucial role in this process, which includes maintaining the balance of fluids and electrolytes within the body. The kidneys have millions of filtration units called nephrons that work in concert with blood vessels to filter blood and produce urine. The urine is then transferred to the urinary bladder via the ureters and is eventually excreted through the urethra.
This system is not only essential for eliminating excess substances but also for maintaining homeostasis, which includes the regulation of blood pressure, the production of hormones, and the balance of pH. The various steps involved in urine formation include filtration, reabsorption, and secretion, which help in maintaining a precise balance of substances and preventing dehydration.