(5.08)

The small glossopharyngeal nerve - this is it - is mainly a sensory nerve. It runs lateral to the internal carotid artery, then passes downward and forward through or lateral to the stylopharyngeus muscle, which it supplies. The glossopharyngeal nerve enters the wall of the pharynx here, between the superior and middle constrictor muscles.

The glossopharyngeal nerve provides sensation, including taste, to the posterior third of the tongue, and also sensation to the back of the oral cavity and the oropharynx.

Now we'll move on to look at the vagus nerve. Its name means wandering: it goes all the way to the abdomen. The principal role of the vagus is to provide parasympathetic supply to organs throughout the thorax and upper abdomen. It also gives sensory and motor supply to the pharynx and larynx.

To see the upper end of the vagus we'll take this nerve, the hypoglossal, out of the picture for now. Here's the vagus. Its trunk is thickened by this ganglion, which is the lower of two.

To follow the vagus in its course down the neck we'll move the internal jugular vein aside. The vagus runs down the neck with the internal jugular vein behind it, and the internal and common carotid arteries in front of it, all the way down to the superior thoracic aperture. The clavicles have been removed in this dissection: here's where they were. Here's the first rib.

The vagus continues down into the thorax: its further course is shown in Tape 3 of this Atlas. The vagus nerve has important branches in the neck. We'll remove the common and internal carotid arteries to see them.

High in the neck the vagus gives off a pharyngeal branch or branches, and this large branch, the superior laryngeal nerve. Right down in the thorax the vagus also gives off the important recurrent laryngeal nerve: we'll come to it in a minute.

The pharyngeal branch or branches of the vagus enter the wall of the pharynx. They supply the superior and middle constictor muscles, and all the muscles of the palate except the tensor palati.

The superior laryngeal nerve passes downwards and forwards towards the hypopharynx. We'll follow the superior laryngeal nerve in another dissection. The hyoid bone is here, the thyroid cartilage is here.

The superior laryngeal nerve - here it is - divides into an external branch, and an internal branch. The internal branch enters the wall of the hypopharynx by passing through the thyrohyoid membrane here. It provides sensation to the hypopharynx, the epiglottis, and the part of the larynx that lies above the vocal folds. The external branch gives motor supply to the cricothyroid muscle and the inferior constrictor muscle.

Now we'll look at the recurrent laryngeal nerve. To see it we'll go to a different dissection in which the internal jugular vein, which was here, has been removed. Here's the common carotid artery, here's the vagus.

Down here the vagus passes in front of the subclavian artery. As it does so it gives off the recurrent laryngeal nerve. As we saw in Tape 3, the recurrent laryngeal nerve goes round the subclavian artery on the right, and round the arch of the aorta on the left.

To see the recurrent laryngeal nerve in this dissection, we'll remove the common carotid artery. Here's the recurrent laryngeal nerve. It runs upwards and medially alongside the trachea, and passes behind the lower pole of the thyroid gland.

To follow its course we'll remove the thyroid gland, and the infrahyoid muscles. Here's the upper end of the trachea, joining the cricoid cartilage, which is here. This is the cricothyroid muscle. Here's the recurrent laryngeal nerve. It runs upwards and reaches the larynx here, behind the arch of the cricoid cartilage.

In its upward course it crosses the branches of the inferior thyroid artery, or runs between them, as in this case. The recurrent laryngeal nerve gives motor supply to all the muscles of the larynx, except the cricothyroid. It also provides sensation to the larynx below the vocal folds.