what is saliva , mucus , gasteric juices

Saliva is a clear liquid secreted into the mouth by the salivary glands and mucous glands of the mouth; moistens the mouth and starts the digestion of starch. It contains the enzyme amylase.

Mucus is the protective, slippery secretion of the mucus membranes; in the gut it lubricates the passage of food and protects the epithelial cells; in the nose and throat and lungs it can make it difficult for bacteria to penetrate the body through the epithelium.

Gastric juices are digestive secretions of the stomach glands consisting chiefly of hydrochloric acid and mucin and the enzyme pepsin (also rennin and lipase.)