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Encyclopedia > Swallowing

Swallowing, known scientifically as deglutition, is the reflex in the human body that makes something pass from the mouth, to the pharynx, into the esophagus, with the shutting of the epiglottis. If this fails and the object goes through the trachea, then choking or pulmonary aspiration can occur. Image File history File links Question_book-3. ... Swallowed was a song by British grunge rock band Bush. ... For other uses, see Mouth (disambiguation). ... The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea. ... The esophagus (also spelled oesophagus/Å“sophagus, Greek ), or gullet is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. ... The epiglottis is a lid-like flap of fibrocartilage tissue covered with a mucus membrane, attached to the root of the tongue. ... Windpipe redirects here. ... For choking meaning compression of the neck, see Strangling. ... In medicine, aspiration is the entry of secretions or foreign material into the trachea and lungs. ...

Contents

Coordination and control

The mechanism for swallowing is co-ordinated by the swallowing centre in the medulla oblongata and pons. The reflex is initiated by touch receptors in the pharynx as a bolus of food is pushed to the back of the mouth by the tongue. The medulla oblongata is the lower portion of the brainstem. ... For other uses, see Pons (disambiguation). ... The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea. ... Look up bolus in Wiktionary, the free dictionary. ...


Swallowing is a complex mechanism using both skeletal muscle (tongue) and smooth muscles of the pharynx and esophagus. The autonomic nervous system (ANS) coordinates this process in the pharyngeal and esophgeal phases. The esophagus (also spelled oesophagus/Å“sophagus, Greek ), or gullet is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. ... This article or section is in need of attention from an expert on the subject. ...


Phases

Normal swallowing consists of four phases: oral preparatory, oral, pharyngeal, and esophageal (not all sources consider oral preparatory a distinct phase).


Oral preparatory phase

In this phase, the food is processed by mastication, combined with the movement of the tongue form a bolus to an appropriate size to pass through the pharynx and esophagus. Mastication or chewing is the process by which food is mashed and crushed by teeth. ... Look up bolus in Wiktionary, the free dictionary. ...


Oral (or "buccal") phase

When the bolus is ready to enter the oral stage, it is first moved to the back of the tongue. Next, the anterior tongue lifts to the hard palate and retracts in a posterior direction to force the bolus to the oropharynx. Then, the posterior tongue is lifted by the mylohyoid muscles, which also elevates the soft palate and seals the nasopharynx to prevent nasal aspiration. This phase is voluntary and involves important cranial nerves: V (trigeminal), VII (facial), and XII (hypoglossal). The pharynx is the part of the digestive system of many animals immediately behind the mouth and in front of the esophagus. ... The nasopharynx (nasal part of the pharynx) lies behind the nose and above the level of the soft palate: it differs from the oral and laryngeal parts of the pharynx in that its cavity always remains patent (open). ... Cranial nerves Cranial nerves are nerves that emerge directly from the brain in contrast to spinal nerves which emerge from segments of the spinal cord. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the middle ear), and other muscles in the floor of the mouth, such as the... The facial nerve is the seventh (VII) of twelve paired cranial nerves. ... The hypoglossal nerve is the twelfth cranial nerve. ...


Pharyngeal phase

In this phase, the bolus is advanced from the pharynx to the esophagus through peristalsis. The soft palate is elevated to the posterior nasopharyngeal wall, through the action of the levator veli palatini. The palatopharyngeal folds on each side of the pharynx are brought close together through the superior constrictor muscles, so that only a small bolus can pass. Then the larynx and hyoid are elevated and pulled forward to the epiglottis to relax the cricopharyngeus muscle. This passively shuts off its entrance and the vocal cords are pulled close together, narrowing the passageway between them. This phase is passively controlled reflexively and involves cranial nerves V, X (vagus), XI (accessory), and XII. Peristalsis is the rhythmic contraction of smooth muscles to propel contents through the digestive tract. ... The hyoid bone (Os Hyoideum; Lingual Bone) is a bone in the human neck, not articulated to any other bone; it is supported by the muscles of the neck and in turn supports the root of the tongue. ... The Inferior pharyngeal constrictor, the thickest of the three constrictors, arises from the sides of the cricoid and thyroid cartilage. ... The space between the vocal cords is called the glottis. ... The vagus nerve (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired cranial nerves, and is the only nerve that starts in the brainstem (within the medulla oblongata) and extends, through the jugular foramen, down below the head, to the abdomen. ... In anatomy, the accessory nerve is a nerve that controls specific muscles of the neck. ...


The respiratory centre of the medulla is directly inhibited by the swallowing centre for the very brief time that it takes to swallow. This is known as deglutition apnoea. Control of ventilation (control of respiration) refers to the physiological mechanisms involved in the control of physiologic ventilation. ...


Esophageal phase

The upper oesophageal sphincter relaxes to let food past, after which various striated constrictor muscles of the pharynx as well as peristalsis and relaxation of the lower esophageal sphincter sequentially push the bolus of food through the esophagus into the stomach. The cardia is the anatomical term for the junction orifice of the stomach and the esophagus. ...


In terminally ill patients, a failure of the reflex to swallow leads to a buildup of mucous or saliva in the throat and airways, producing a noise known as a death rattle, or agonal respiration. A death rattle is a gurgling or rattle-like noise produced by the accumulation of excessive respiratory secretions in the throat. ... Agonal respiration is an abnormal pattern of breathing characterized by shallow, slow (3-4 per minute), irregular inspirations followed by irregular pauses. ...


Clinicial significance

Swallowing becomes a great concern for the elderly since strokes and Alzheimer's disease can interfere with the ANS. Speech therapy is commonly used to correct this condition since the speech process uses the same neuromuscular structures as swallowing. It has been suggested that Speech-Language Pathology, Speech pathology, Phoniatrics be merged into this article or section. ...


Disorders of the oral or pharyngeal phases may lead to oropharyngeal dysphagia and disorders of the esophageal may lead to esophageal dysphagia. Dysphagia should not be confused with the similarly pronounced dysphasia, a speech disorder. ... Dysphagia should not be confused with the similarly pronounced dysphasia, a speech disorder. ...


See also

Dysphagia () is a medical term defined as difficulty swallowing. ...

External links

  • Physiology at MCG 6/6ch3/s6ch3_15
  • Overview at nature.com
  • Anatomy and physiology of swallowing at dysphagia.com
  • swallowing animation (flash) at hopkins-gi.org

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