(1.45)

Now we'll move on to look at the third, fourth and sixth cranial nerves: the oculomotor, trochlear, and abducent. They're motor nerves. Between them they supply the six muscles that move the eye, and also the levator of the upper lid. As we've seen, the oculomotor nerve arises between the cerebral peduncles, the trochlear nerve arises from the back of the midbrain, and the abducent nerve arises below the pons.

The bony opening that these three nerves pass through is the superior orbital fissure, but their openings in the dura are quite a bit further back. The oculomotor nerve passes through the dura just alongside the posterior clinoid process, which is here. The trochlear nerve passes through the dura here, the abducent nerve down here.

To follow them we'll remove the dura over this area. We'll also remove this structure that we'll see later, the trigeminal ganglion.

This cavity that we've opened into is the cavernous sinus. In the living living body it's filled with venous blood. Within the cavernous sinus lies the internal carotid artery.

The third, fourth and sixth nerves pass forward in the lateral wall of the cavernous sinus. Here's the oculomotor, here's the trochlear, here's the abducent. All three nerves pass forward into the orbit through the superior orbital fissure, which is here.