Nucleus ambiguus

The nucleus ambiguus is a large longitudinal nucleus within the medulla oblongata that provides motor innervation to muscles of the pharynx, larynx and soft palate in addition to housing preganglionic nuclei involved in parasympathetic nervous system augmentation of heart rate .

Gross anatomy

The nucleus ambiguus is a paired nucleus located in the lateral aspect of the rostral medulla.

It lies dorsal to the inferior olivary nucleus and ventromedial to the spinal nucleus and tract of the trigeminal nerve (CN V). It is located medial to the lateral spinothalamic tract.

The dorsal motor nucleus of the vagus nerve (CN X) and the solitary tract nucleus both lie dorsal to the nucleus ambiguus, and their respective fibers course around the dorsolateral aspect of the nucleus ambiguus.

Innervation

The nucleus ambiguus houses cell bodies which provide motor fibers to the glossopharyngeal (CN IX), vagus (CN X) and spinal accessory nerves (CN XI), which pass laterally from the nucleus ambiguus to exit the medulla in the postolivary sulcus.

The nucleus ambiguus provides motor innervation to the stylopharyngeus muscle with the efferent fibers traveling within the glossopharyngeal nerve (CN IX).

The nucleus ambiguus also provides motor innervation to the superior, middle and inferior pharyngeal constrictor muscles in addition to the muscles of the soft palate (palatopharyngeus, salpingopharyngeus, levator veli palatini, palatoglossus and the muscles of the uvula). These efferent fibers arising from the nucleus ambiguus travel through pharyngeal branches of the vagus nerve (CN X) which arise from the inferior (nodose) vagal ganglion.

The external laryngeal nerve supplies the cricothyroid muscle (the only intrinsic muscle of the larynx not supplied by the recurrent laryngeal nerve).

The recurrent laryngeal nerve provides motor innervation to all of the intrinsic laryngeal muscles except the cricothyroid muscle.

The nucleus ambiguus also houses preganglionic neurons which contribute to vagal parasympathetic control of heart rate.