Mastication(chewing) The teeth are designed for chewing. Chewing reflex Presence of a bolus of food in the mouth Initiates reflex inhibition of the muscles of mastication Lower jaw drops. Initiates a stretch reflex of the jaw muscles Rebound contraction. Automatically Jaw raised Closure of the teeth Compresses the bolus again against the linings of the mouth

Neural Control Muscles of chewing - innervated by the motor branch of the fifth cranial nerve. The chewing process is controlled by nuclei in the brain stem. Stimulation of specific reticular areas in the brain stem taste centers - rhythmical chewing movements. Stimulation of areas in the Hypothalamus, Amygdala, and even the Cerebral cortex near the sensory areas for taste and smell cause chewing.

Functions of Mastication Chewing is important for digestion of fruits and raw vegetables – Indigestible cellulose membranes around their nutrient portions that must be broken Digestive enzymes act only on the surfaces of food particles Rate of digestion increased (Dependent on the total surface area exposed to the digestive secretions) Prevents excoriation of the gastrointestinal tract

Salivary Secretion Saliva is secreted by Parotid gland Sub mandibular gland Sub lingual gland Buccal glands

Saliva Saliva contains two major types of protein secretion Serous secretion (ptyalin) Mucus secretion (mucin)

Saliva has a pH between 6.0 and 7.0. Daily secretion of saliva is between 800ml and 1500ml (average 1000ml)

Regulation of salivary secretion