![]() ![]() Nucleus solitarius receives the baroreceptor sensory input, while the nucleus ambiguus (and dorsal motor nucleus to a lesser extent) are involved in the parasympathetic output. The vagus nerve, which has various motor, sensory, and autonomic functions involving multiple organ systems, is associated with three main nuclei in the brainstem: the dorsal motor nucleus, nucleus ambiguus, and nucleus solitarius. The muscles controlled by the nucleus ambiguus initiate the mechanism of swallowing and phonation.Īdditionally, the nucleus contributes to parasympathetic cardiac regulation. It gives rise to the efferent motor fibers of the vagus nerve (CN X) that innervate the muscles of the soft palate, larynx, pharynx, as well as the stylopharyngeus muscles and pharyngeal constrictor muscles of the glossopharyngeal nerve (CN IX). The nucleus ambiguus is involved in the motor functions of swallowing and speech. The nuclei are in the lateral regions of the rostral medulla posterior to the inferior olive. Its location is in the reticular formation of the medulla oblongata, the lowest part of the brainstem. The nucleus ambiguus is the location of cell bodies of motor nerves that innervate the ipsilateral muscles of the soft palate, pharynx, larynx and upper esophagus and are mainly responsible for swallowing and speaking. Unilateral lesions of the nucleus ambiguus may lead to dysphagia and hoarseness, and these characteristics are classic in lateral medullary syndrome (Wallenberg syndrome). Additionally, the nucleus ambiguus plays a role in parasympathetic cardiac inhibition through CN X. The nucleus ambiguus provides fibers that innervate the somatic muscles of the pharynx, larynx, and soft palate. Its location is in the reticular formation in the medulla oblongata. The name ‘ambiguus’ originates from its difficult-to-find location and variation in different species. Killian dehiscence is the most common site of pharyngeal diverticula 5.The nucleus ambiguus is the common nucleus of the efferent fibers for glossopharyngeal (CN IX) and vagus (CN X) nerves. The increased intraluminal pressures then lead to herniation through this potential area of weakness 1,5. Uncoordinated contraction of the inferior pharyngeal constrictor and spasm, or fibrosis, of cricopharyngeus, have been implicated in the formation of pharyngeal pouches (Zenker diverticula), due to the increased intraluminal pressures these cause during swallowing. It is named after Gustav Killian (1860-1921) a German otolaryngologist. ![]() As the pharyngeal constrictors (apart from cricopharyngeus) are attached to the median raphe, which in turn is attached to the skull base, laryngeal descent during development causes the constrictors to assume an oblique course, leaving cricopharyngeus in a transverse orientation, thus creating a potential area of weakness 4. Killian dehiscence arises due to the descent of the larynx during development 4. This could explain why pharyngeal pouches are more common in males. One study suggests that it is present in ~60% of males, and just ~30% of females 3. The dimensions of Killian's triangle of weakness have also been shown to correlate with individual anthropometric parameters, consequently being more prominent in males than in females 3. While not anatomically evident in every individual, it has been found to occur more commonly in males 3. ![]()
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