Final answer:
The kidneys filter the blood and remove the major substances including urea, excess salt, and excess water to maintain the body's homeostasis. Urea is a waste product from protein metabolism, while salt and water are regulated to maintain fluid balance. Carbon dioxide is mostly removed by the lungs and sugars and proteins are normally reabsorbed, not excreted by the kidneys.
Step-by-step explanation:
The kidneys are essential organs in the urinary system responsible for filtering the blood and removing various substances to maintain the body's homeostasis. The three major substances removed from the blood by the kidneys are urea, excess salt, and excess water. Urea is a nitrogenous waste product that comes from the metabolism of proteins, and it's the primary waste that the kidneys filter out of the blood. Salt, which includes various minerals, and excess water are also eliminated to regulate the body's fluid balance and ensure proper cellular function.
The kidneys help in maintaining the acid-base balance by regulating pH through the secretion or reabsorption of hydrogen ions and bicarbonate. They also play a pivotal role in regulating blood pressure and are involved in the reabsorption of important substances, such as calcium, sodium, glucose, and amino acids to maintain homeostatic plasma concentrations.