单词 | swallowing |
释义 | swallowingswal·low 1S0930700 (swŏl′ō)swal·low 2S0930700 (swŏl′ō)SwallowingSwallowinga complex reflex act in which food is carried from the oral cavity to the esophagus and stomach by the contraction of some muscles and the relaxation of others. In vertebrates and man, the swallowing reflex arises upon stimulation of the sensitive endings of the trigeminal, superior and inferior laryngeal, and glossopharyngeal nerves in the mucous membrane of the soft palate. The swallowing center is located on the floor of the fourth ventricle in the medulla oblongata. The first phase of swallowing is voluntary. The lump of chewed food is pushed into the pharynx by movements of the cheeks and tongue. Contraction of the palatine arches and radix linguae, closure of the nasopharyngeal cavity, and covering of the entrance to the larynx by the epiglottis allow the bolus to be pushed only into the opening of the esophagus, whose peristaltic movements provide for its further passage. Swallowing ends with relaxation of the muscular closure and entrance to the stomach. Liquid passes through the esophagus under the influence of pressure created in the pharynx and its own weight. swallowingswallowing[swahl´o-ing]Normally, air is free to pass from the nose or mouth to the lungs and back again. But the moment the bolus approaches the fauces, the passage from the mouth to the pharynx, nerve centers are triggered that control a series of reflex actions. After one quick inhalation, breathing is halted for the brief instant of the next stage. In this second, involuntary, stage of swallowing, the rear edge of the soft palate, which hangs down from the roof of the mouth, swings up against the back of the pharynx and blocks the passages to the nose. The back of the tongue fits tightly into the space between two muscular pillars at each side of the fauces, sealing the way back to the mouth. Simultaneously, the larynx moves upward against the epiglottis, effectively closing the entrance to the trachea. Sometimes the larynx does not move up quickly enough and food gets into the air passage, stimulating a coughing reaction. With the one-way route to the stomach firmly established, however, the muscular coat of the pharynx contracts, squeezing the ball of food and forcing its passage into the esophagus. In the third stage, the rhythmic contraction (peristalsis) of the muscles of the esophagus moves the food on to the stomach. The cardiac sphincter keeps the stomach entrance closed until food is swallowed. As the food approaches, moved by the wavelike contractions of the esophagus, the advancing portion of the wave causes the sphincter to relax and open, while the rear and contracting portion forces the ball of food through the entrance. swallowingS24-922280 (swal'o-ing)![]() In the first stage, food is placed on the surface of the tongue. The tip of the tongue is placed against the hard palate; then elevation of the larynx and backward movement of the tongue forces food through the isthmus of the fauces in the pharynx. In the second stage, the food passes through the pharynx. This involves constriction of the walls of the pharynx, backward bending of the epiglottis, and an upward and forward movement of the larynx and trachea. This may be observed externally with the bobbing of the Adam's apple. Food is kept from entering the nasal cavity by elevation of the soft palate and from entering the larynx by closure of the glottis and backward inclination of the epiglottis. During this stage, respiratory movements are inhibited by reflex. In the third stage, food moves down the esophagus and into the stomach. This movement is accomplished by momentum from the second stage, peristaltic contractions, and gravity. With the body in an upright position, liquids pass rapidly and do not require assistance from the esophagus. However, second-stage momentum and peristaltic contractions are sufficient to allow liquids to be drunk even when the head is lower than the stomach. Difficulty in swallowing is called dysphagia. See: dysphagia; illustration air swallowingimpaired swallowingtongue swallowingSee: tongue-swallowingPatient discussion about swallowingQ. Is it dangerous to swallow a bubble gum? My 4 year old child always swallows his chewing gum and I am worried that it can harm him Q. Why is it hard to swallow when you have a sore throat? I was sick last week. I had a sore throat pain in my neck and fever. the most annoying symptom that i had was pain during sallowing. what is the source of that pain, and what can I do to ease it next time? Q. mouth ulcer and difficulty to swallow, below right side of inner tongue guggle salt water and vinigar dose'nt help |
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