The tenth cranial nerve, and one of the most important, is the vagus nerve. All twelve of the cranial nerves, the vagus nerve included, emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column. The vagus nerve originates in the medulla oblongata, a part of the brain stem.
The vagus nerve is a remarkable nerve that relates to the function of numerous structures in the body. The vagus nerve supplies nerve fibers to the pharynx (throat), larynx (voice box), trachea (windpipe), lungs, heart, esophagus and most of the intestinal tract (as far as the transverse portion of the colon). And the vagus nerve brings sensory information back from the ear, tongue, pharynx and larynx.
The term “vagus” (Latin for “wandering”) is apt because the vagus nerve wanders all the way down from the brainstem to the colon, a long wandering trek.
Complete interruption of the vagus nerve causes a characteristic syndrome. The back part of the palate (the soft palate) droops on that side. The capacity to gag (the gag reflex) is also lost on that side. The voice is hoarse and nasal. The vocal cord on the affected side is immobile. The result is dysphagia and dysphonia (trouble swallowing and trouble speaking).
One of the best known branches of the vagus nerve is the recurrent laryngeal nerve. After leaving the vagus nerve, the recurrent laryngeal nerve goes down into the chest and then loops back up to supply the larynx (the voice box). Damage to the recurrent laryngeal nerve can result from diseases inside the chest (intrathoracic diseases) such as a tumor or an aneurysm (ballooning) of the arch of the aorta or of the left atrium of the heart. The consequence is laryngeal palsy, paralysis of the larynx (the voice box), on the affected side. Laryngeal palsy can also be caused by damage to the vagus nerve before it gives off the recurrent laryngeal nerve.
- Nerve, third cranial
The upper eyelid muscle which raises the eyelid; The extraocular muscle which moves the eye inward; and The pupillary muscle which constricts the pupil. Paralysis of the oculomotor nerve results in drooping eyelid (ptosis), deviation of the eyeball outward (and therefore double vision) and a dilated (wide-open) pupil.
- Nerve, trigeminal
This nerve functions both as the chief nerve of sensation for the face and as the motor nerve controlling the muscles of mastication (chewing). Problems with the sensory part of the trigeminal nerve result in pain or loss of sensation in the face. Problems with the motor root of the trigeminal nerve result in deviation […]
- Nerve, trochlear
The trochlear nerve controls the superior oblique muscle of the eye, one of the extraocular muscles, the muscles that move the eye. Paralysis of the trochlear nerve results in rotation of the eyeball upward and outward (and, therefore, double vision). The trochlear nerve is the fourth cranial nerve. (The twelve cranial nerves emerge from or […]
- Nerve, vagus
A remarkable nerve that supplies nerve fibers to the pharynx (throat), larynx (voice box), trachea (windpipe), lungs, heart, esophagus, and the intestinal tract as far as the transverse portion of the colon. The vagus nerve also brings sensory information back to the brain from the ear, tongue, pharynx, and larynx. The vagus nerve is the […]
- Nerve, vestibulocochlear
A nerve that is responsible for the sense of hearing and which is also pertinent to balance, to the body position sense. Problems with the vestibulocochlear nerve may result in deafness, tinnitus (ringing or noise in the ears), dizziness, vertigo and vomiting. The vestibulocochlear nerve is the eighth cranial nerve. The 12 cranial nerves, the […]