CBSE Class 10 Answered

Food enters the mouth and is chewed by the teeth, turned over and mixed with saliva by the tongue. Chewing breaks food into smaller particles so that chemical digestion can occur faster. The sensations of smell and taste from the food sets up reflexes which stimulate the salivary glands. These glands increase their output of secretions through three pairs of ducts into the oral cavity, and begin the process of digestion. Saliva lubricates the food, thus enabling it to be swallowed. It contains the enzyme amylase (ptyalin) which breaks starch (a polysaccharide) down to maltose (a disaccharide). Bicarbonate ions in saliva act as buffers, maintaining a pH between 6.5 and 7.5. Mucins (mucous) lubricate and help hold chewed food together in a clump called a bolus. The tongue contains chemical receptors in structures called taste buds. The tongue is muscular and can move food. It pushes food to back where it is swallowed.