The excretory organ that removes salt is the kidney. The kidneys are responsible for filtering waste products from the blood and regulating the body's fluid balance. They play a crucial role in maintaining the proper levels of electrolytes, including sodium (salt), potassium, and chloride, in the body.

Inside the kidneys, specialized structures called nephrons are responsible for the filtration and reabsorption of various substances. When blood enters the kidneys, the nephrons filter out waste products, excess water, and electrolytes. As the filtered fluid moves through the nephrons, essential substances like glucose, amino acids, and most of the filtered sodium are reabsorbed back into the bloodstream.

However, some sodium is actively secreted by the kidneys to maintain the body's sodium balance. This secretion occurs in specific parts of the nephrons, mainly in the collecting ducts. The kidneys can adjust the amount of sodium excreted based on the body's needs. For example, in cases of dehydration or low blood volume, the kidneys conserve sodium by reabsorbing more of it, reducing its excretion. Conversely, in conditions of excess fluid volume or high blood pressure, the kidneys increase sodium excretion to help eliminate excess fluid and lower blood pressure.

Therefore, the kidneys play a critical role in regulating sodium levels in the body and ensuring proper fluid balance and electrolyte homeostasis.