Digestive secretions are secreted only when needed. Discuss.

Explanation

Digestive glands are excerine glands which secrete biological catalysts called enzymes. These enzyme convert the complex, insoluble food materials like carbohydrates, proteins and lipids into simplex, soluble food materials like glucose and fructose, amino acids and fatty acids and glycerol. These digestive secretions act only when food materials are available in the alimentary canal