Which one of the following elements is involved in the control of water content of the blood?

Potassium is a vital electrolyte involved in the control of water content and fluid balance in the human body. It is the most abundant intracellular cation, playing a critical role in maintaining intracellular fluid volume. Along with sodium, which regulates extracellular fluid, potassium helps maintain the osmotic balance between cells and interstitial fluid [5]. Electrolytes like potassium carry an electric charge when dissolved in body fluids, including blood, and are essential for balancing the amount of water in the body [1]. The kidneys regulate the excretion of potassium to maintain consistent total body water and osmolarity. While other alkali metals like lithium, rubidium, and caesium exist, they do not serve as primary physiological regulators of water balance in the blood. Therefore, potassium is the element responsible for controlling water content and maintaining healthy blood volume [2].

Sources

1. [5] https://www.sciencedirect.com/science/article/pii/B9780750633659500109
2. [1] https://medlineplus.gov/fluidandelectrolytebalance.html
3. [2] https://www.cdc.gov/salt/sodium-potassium-health/index.html