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Mastication(chewing)

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

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Mastication(chewing)

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  1. 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

  2. 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.

  3. 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

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

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

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

  7. Regulation of salivary secretion

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