What fluid in the mouth contains water, electrolytes, mucus and enzymes?

• A. Saliva
• B. Mucus
• C. Blood
• D. Gastric juice

Answer: (A)

Saliva is the fluid produced by the salivary glands in the mouth. It is mostly water, but also contains electrolytes that help maintain pH and mineral balance, mucus (mucin) to lubricate and make swallowing easier, and enzymes such as salivary amylase that start digesting starches right away. This combination keeps the mouth moist, protects teeth, and aids the initial step of digestion. The other fluids listed don’t fit: mucus is mainly a lubricating secretion without enzymes, blood is a circulatory fluid not normally secreted into the mouth, and gastric juice is stomach fluid for digestion, not a mouth secretion. Therefore, the fluid in the mouth with water, electrolytes, mucus, and enzymes is saliva.