Salivation: the secretion of saliva is controlled by the ANS. Normally, parasympathetic stimulation promotes continuous secretion daily keeping the mucus membranes moist and lubricates the movements of the tongue and lips during vocalization. Saliva is then swallowed and helps moisten the esophagus. It is then reabsorbed preventing fluid loss. Sympathetic stimulation dominates during stress resulting in dryness of mouth. If your body becomes dehydrated, the salivary glands stop secreting saliva to conserve water resulting in dryness of the mouth and thirst. Drinking restores the homeostasis of body water and also moistens the mouth. The feel and taste of food are potent stimulators of salivary secretion. Chemicals in the food stimulate receptors in taste buds of the tongue, and impulses are conveyed from the taste buds to salivary nuclei in the brain. Parasympathetic fibres return impulses (facial VII) and glossopharyngeal (IX) to stimulate secretion of saliva. Smell, sight, sound, or thought of food may also stimulate secretion of saliva.
Digestion in the Mouth
Mechanical digestion results from chewing or Mastication in which food is manipulated by the tongue, ground by the teeth, and mixed with saliva. The result is a mass of food called a Bolus ; food molecules begin to dissolve in the water in saliva.
Pharynx
Food passes from the mouth to the pharynx (throat). Composed of skeletal muscle and lined by a mucus membrane. Composed of: Nasopharynx, Oropharynx, Laryngopharynx Oropharynx and Laryngopharynx have digestive functions. Muscular contractions of these two areas help to propel food into the esophagus and then into the stomach. Once the bolus is formed, it is pushed to the back of the pharynx for swallowing. The soft palate, a muscular continuation of the hard palate, separates the esophagus and the larynx. During breathing the epiglottis lies on top of the soft palate and allows air into the larynx. During swallowing the epiglottis covers the larynx and the soft palate rises to allow food into the esophagus.
Deglutition
Movement of food from the mouth into the stomach is achieved by swallowing or Deglutition . Deglutition Centre located in the Medulla Oblongata and lower Pons Deglutition is facilitated by the secretion of saliva and mucus and involves the mouth, pharynx, and esophagus. Swallowing occurs in 3 stages:
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