Which process maintains homeostasis of fluid levels in the body?

Osmoregulation is the process responsible for maintaining homeostasis of fluid levels in the body. This involves regulating the balance of water and electrolytes, ensuring that the internal environment of the organism remains stable despite changes in external conditions. It includes mechanisms that control the movement of water across cell membranes, as well as the regulation of salts and other solutes in bodily fluids.

One of the key components of osmoregulation is the function of the kidneys in vertebrates, which filter blood to remove wastes and excess substances, producing urine that can expel these components while conserving water when necessary. This regulatory function is crucial for maintaining blood pressure, proper cellular function, and overall fluid balance, which is vital for health and survival.

In contrast, respiration refers to the process of gas exchange, where oxygen is taken in and carbon dioxide is expelled, which is crucial for energy production but does not directly address fluid levels. Metabolism encompasses all chemical reactions in the body, including those that provide energy, build up molecules, and break them down, but it also does not specifically focus on fluid regulation. Digestion involves breaking down food into nutrients, which is part of the overall process of obtaining energy, rather than regulating fluid levels. Thus, osmoregulation