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Chapter 3: Respiratory Anatomy and Physiology

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A patient requires an awake fiberoptic intubation. The anesthesia team elects to perform the procedure via the nasotracheal route. In order to anesthetize the nasal mucosa, which of the following nerves must be blocked?

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(A) olfactory nerve

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(B) facial nerve

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(C) trigeminal nerve

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(D) glossopharyngeal nerve

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(E) vagus nerve

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The answer is C. Sensation to the nasal cavity is supplied by the V1 and V2 branches of the trigeminal nerve (cranial nerve V). The V1 branch of the trigeminal nerve, the ophthalmic nerve, branches into the anterior ethmoidal nerve which provides sensation to the anterior portion of the nasal septum. The V2 branch of the trigeminal nerve, the maxillary nerve, branches into the greater and lesser palatine nerves which provide sensation to the nasal turbinates and majority of the nasal septum. The glossopharyngeal nerve (cranial nerve IX) provides sensation to the pharynx, posterior third of the tongue, anterior surface of epiglottis, and tonsils. The vagus nerve (cranial nerve X), via the internal branch of the superior laryngeal nerve, provides sensation to the root of the tongue, posterior epiglottis, arytenoids, and aryepiglottic folds. The vagus nerve, via the recurrent laryngeal nerve, provides sensation to the vocal folds and trachea. The olfactory nerve (cranial nerve I) is responsible for sense of smell. A branch of the facial nerve (cranial nerve VII) is responsible for sense of taste on the anterior two thirds of the tongue, while the glossopharyngeal nerve is responsible for sense of taste on the posterior third of the tongue.

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Ref: Hadzic A. NYSORA Textbook of Regional Anesthesia and Acute Pain Medicine. 1st ed. New York, NY: McGraw Hill; 2007.

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In the emergency department, an unconscious trauma patient is evaluated before transfer to the operating room. Suction to the back of the patient's throat does not elicit a gag reflex. Which of the following nerves innervates the sensory portion of this reflex?

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(A) trigeminal nerve

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(B) glossopharyngeal nerve

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(C) vagus nerve

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(D) facial nerve

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(E) hypoglossal nerve

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The answer is B. The sensory (afferent) portion of the gag reflex is mediated by the glossopharyngeal nerve (cranial nerve IX). The motor (efferent) portion of the gag reflex is mediated by the vagus nerve (cranial nerve X). Overall, touching the posterior pharyngeal wall elicits elevation of the soft palate and pharyngeal muscle contraction. The V2 (maxillary) branch ...

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