TAILIEUCHUNG - Chapter 034. Cough and Hemoptysis (Part 1)

Harrison's Internal Medicine Chapter 34. Cough and Hemoptysis Cough Cough is an explosive expiration that provides a normal protective mechanism for clearing the tracheobronchial tree of secretions and foreign material. When excessive or bothersome, it is also one of the most common symptoms for which patients seek medical attention. Reasons for this include discomfort from the cough itself, interference with normal lifestyle, and concern for the cause of the cough, especially fear of cancer. Mechanism Coughing may be initiated either voluntarily or reflexively. As a defensive reflex it has both afferent and efferent pathways. . | Chapter 034. Cough and Hemoptysis Part 1 Harrison s Internal Medicine Chapter 34. Cough and Hemoptysis Cough Cough is an explosive expiration that provides a normal protective mechanism for clearing the tracheobronchial tree of secretions and foreign material. When excessive or bothersome it is also one of the most common symptoms for which patients seek medical attention. Reasons for this include discomfort from the cough itself interference with normal lifestyle and concern for the cause of the cough especially fear of cancer. Mechanism Coughing may be initiated either voluntarily or reflexively. As a defensive reflex it has both afferent and efferent pathways. The afferent limb includes receptors within the sensory distribution of the trigeminal glossopharyngeal superior laryngeal and vagus nerves. The efferent limb includes the recurrent laryngeal nerve and the spinal nerves. The cough starts with a deep inspiration followed by glottic closure relaxation of the diaphragm and muscle contraction against a closed glottis. The resulting markedly positive intrathoracic pressure causes narrowing of the trachea. Once the glottis opens the large pressure differential between the airways and the atmosphere coupled with tracheal narrowing produces rapid flow rates through the trachea. The shearing forces that develop aid in the elimination of mucus and foreign materials. Etiology Cough can be initiated by a variety of irritant triggers either from an exogenous source smoke dust fumes foreign bodies or from an endogenous origin upper airway secretions gastric contents . These stimuli may affect receptors in the upper airway especially the pharynx and larynx or in the lower respiratory tract following access to the tracheobronchial tree by inhalation or aspiration. When cough is triggered by upper airway secretions as with postnasal drip or gastric contents as with gastroesophageal reflux the initiating factor can go unrecognized and the cough may persist. Additionally .

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