In physiology, the term serous fluid is used for various bodily fluids that are typically pale yellow and transparent, and of a benign nature.
Saliva consists of mucus and serous fluid; the serous fluid contains the enzyme amylase important for the digestion of carbohydrates. Minor salivary glands of von Ebner present on the tongue secrete the amylase. The parotid gland produces purely serous saliva. The other major salivary glands produce mixed (serous and mucus) saliva.
Another type of serous fluid is secreted by the serous membranes (or serosa), two layered membranes which line the body cavities. The serous fluid between the two layers acts as a lubricant and reduces friction from muscle movement.