Let's move on to look at the last four cranial nerves. They're the glossopharyngeal, number nine, the vagus, number ten, the accessory, number eleven, and the hypoglossal, number twelve. These four nerves leave the skull close together.
Here are the ninth, tenth and eleventh nerves. The ninth and tenth nerves arise from a line of filaments that emerge from the lateral aspect of the medulla.
Here's the glossopharyngeal nerve, the ninth cranial nerve. It's quite small. Below it is the vagus, the tenth nerve, arising by one large root, and a line of smaller ones that emerge from the medulla all the way down to here.
Below the vagus, is the accessory nerve. Its full name is the spinal accessory. It arises from a procession of filaments that emerge from the spinal cord from C1 as far down as C5. The spinal accessory runs upwards through the foramen magnum to join the ninth and tenth nerves.
The hypoglossal nerve, the twelfth cranial nerve, arises more anteriorly. Here are its filaments converging. The hypoglossal nerve passes through the dura by itself, the ninth, tenth and eleventh nerves pass through the dura together to enter the jugular foramen.
Nerves nine, ten and eleven leave through this part of the jugular foramen. The hypoglossal nerve leaves through this opening, the hypoglossal canal.
We'll go round to the outside of the skull to see where the nerves emerge. Here's the jugular foramen, with the hypoglossal canal opening just in front of it. Nerves IX, X and XI emerge through this part of the jugular foramen.
Here are the four nerves emerging in front of the upper end of the internal jugular vein. Here's the internal carotid artery, the styloid process was here.
Here's the glossopharyngeal nerve, here's the vagus, here's the accessory, here's the hypoglossal. To get this view we've removed the styloid process and its muscles, the posterior belly of the digastric muscle, and the ramus of the mandible, as we did in the last section.
We'll follow these four nerves one at a time, adding or removing the overlying structures as we progress.