Nucleus ambiguus

The nucleus ambiguus is a cluster of large motor neurons located deep within the medullary reticular formation of the brainstem.

Afferent Connections:

The nucleus ambiguus receives upper motor neuron input through the corticobulbar tract, with contributions from both cerebral hemispheres.

Efferent connections:

The motor neurons of the nucleus ambiguus give rise to branchial efferent fibers that travel via the glossopharyngeal (CN IX), vagus (CN X), and cranial root of the accessory nerve (CN XI). These fibers innervate muscles of the soft palate, pharynx, and larynx, which are crucial for functions such as speech and swallowing.

• Via the Glossopharyngeal Nerve: Efferent fibers from the nucleus ambiguus innervate the stylopharyngeus muscle, one of the longitudinal muscles of the pharyngeal wall.

• Via the Vagus Nerve: Neurons from the nucleus ambiguus innervate both the constrictor muscles of the pharynx (superior, middle, and inferior) and the longitudinal pharyngeal muscles (palatopharyngeus and salpingopharyngeus). Additionally, they supply the intrinsic muscles of the larynx.

• Via the Cranial Root of the Accessory Nerve: Efferent fibers travel with the accessory nerve before joining the vagus nerve to be distributed through its pharyngeal and recurrent laryngeal branches to the muscles of the soft palate, pharynx, and larynx.

This intricate network of connections underlies the critical roles of the nucleus ambiguus in coordinating complex motor functions such as swallowing, phonation, and breathing.