What substance do kidneys remove from the blood?

The kidneys play a crucial role in maintaining the body's homeostasis, primarily through the filtration of blood and the regulation of various substances. Among these substances, salts are significant as they help in maintaining fluid and electrolyte balance within the body. The kidneys filter large volumes of blood, removing excess electrolytes—including sodium, potassium, and chloride—along with waste products, while reabsorbing what the body needs to maintain a healthy balance.

This function is essential for regulating blood pressure and pH levels, and it enables the body to excrete waste in the form of urine. While hormones and other bodily systems also regulate these processes, the kidneys' ability to specifically manage salts through filtration and reabsorption is a key part of their overall function in the urinary system.

In contrast, platelets are components of blood involved in coagulation, oxygen is a gas transported by hemoglobin in red blood cells, and glucose is primarily reabsorbed in the kidneys rather than removed, making none of these options applicable in the same context as salts in the kidney's filtering process.