Physiology : a manual for students and practitioners . ay be mechanical or chemical or mental; thus the flowof saliva is increased by taking food into the mouth or by irritat-ing the inside of the mouth by scratching or burning, or by lookingat or smelling or even thinking about food. In the submaxillary gland the chorda tympani nerve is said tohave a double function—to increase the vascularity of the glandby one portion of its fibres, and to excite the secreting function byanother set of fibres, the sympathetic nerves of the gland acting asthe vaso-constrictors. In the parotid the vaso-dilato
Physiology : a manual for students and practitioners . ay be mechanical or chemical or mental; thus the flowof saliva is increased by taking food into the mouth or by irritat-ing the inside of the mouth by scratching or burning, or by lookingat or smelling or even thinking about food. In the submaxillary gland the chorda tympani nerve is said tohave a double function—to increase the vascularity of the glandby one portion of its fibres, and to excite the secreting function byanother set of fibres, the sympathetic nerves of the gland acting asthe vaso-constrictors. In the parotid the vaso-dilator impulse comes also from the facialnerve through the fifth by the communication of the lesser petrosalnerve. The vaso-constrictor impulse comes from the sympathetic. There is found a medullary centre which controls this function. Describe an act of deglutition. Deglutition, or swallowing, is the process by which we conveyfood from the mouth to the stomach, and may be divided for thepurpose of analysis into three actions: 1st. The food after masti-. 45 Human Alimentary Canal: n, a?sophaf;us; /), stomach ; c, cardiac orifice; d, pylorus; e,small intestine; /, biliary duct; ;;, pancreatic duct; h, ascending colon; /, transversecolon; j, descending colon ; k, rectum. 46 DIGESTION. cation is pushed by the tongue against the palate, and so forced ontoward the fauces. 2d. As soon as the bolus enters the pharynx itis pushed on by the tongue and by the contraction of the pillarsof the fauces and the constrictors of the pharynx toward theoesophageal opening. The pharyngeal vault is guarded from in-vasion by solid or liquid food by the valve-action of the soft palate,while the opening of the glottis is protected by the simulta-neous intrinsic muscular closure of the rima glottidis and by thevalve-like cover of the epiglottis. When the muscles of the faucesand tongue push on the food-mass, they also draw up the larynxand dilate the oesophageal opening. 3d. The oesophagus grasps thefood,
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysiology, bookyear1
