What element is considered a major extracellular anion in the body?

Chloride is recognized as a major extracellular anion in the body primarily due to its significant presence in extracellular fluid, where it plays a vital role in maintaining osmotic balance and electrical neutrality. It is commonly found in the form of ions that associate with sodium to help regulate fluid balance and is involved in various physiological processes including the formation of gastric acid in the stomach and facilitating nerve transmission. While sodium is an important extracellular cation and potassium is a major intracellular cation, chloride specifically serves as the predominant anion in the extracellular environment, accentuating its critical role in the overall electrolyte balance of body fluids. Additionally, calcium, while not directly involved as a major anion, contributes to cellular signaling and muscle contraction but does not serve the same role as chloride in extracellular fluid.