Presentation on theme: "Mastication(chewing)"— Presentation transcript:
1 Mastication(chewing) The teeth are designed for chewing.Chewing reflexPresence of a bolus of food in the mouthInitiates reflex inhibition of the muscles of masticationLower jaw drops.Initiates a stretch reflex of the jaw musclesRebound contraction.Automatically Jaw raisedClosure of the teethCompresses the bolus again against the linings of the mouth
2 Neural ControlMuscles 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 theHypothalamus, 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 brokenDigestive enzymes act only on the surfaces of food particlesRate 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 glandSub lingual glandBuccal 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)