 Good day everybody. This is Dr. Sanjay Sanyal, Professor of Department Chair. This is going to be a demonstration of the lower four cranial nerves, C9, 10, 11 and 12 on the right side of the neck. We have completely dissected out the lateral cervical region, anterior cervical region of the supine cadaver right side of the neck. We have removed the ramus of the mandible to show you the intrataprolforcer. We removed the clavicle to show the root of the neck and we removed the sternocleidomaster here. The lower four cranial nerves, let's start with this one here that we can see very clearly. This is the 11th cranial nerve, the spinal accessory. The spinal accessory nerve as you know has got two components, accessory nerve, the spinal and the cranial part. The spinal accessory part comes from C1, 2, 3, 4, 5, sometimes 6. And the fibers they go up through the furamen magnum into the posterior cranial fursum. There it unites temporarily with the cranial accessory which comes from the nucleus ambiguous. And shortly thereafter, when it emerges through the jugular furamen, it separates off. And the cranial accessory emerges with the vagus. And there it forms what is known as the vagus accessory complex. And the remaining part of the accessory comes out. This is the spinal accessory. The spinal accessory nerve, it runs in front of the internal jugular vein. And then it enters onto the deep surface of the sternocleidomaster. And we can see that very clearly here. It supplies the sternocleidomaster. And after it has supplied the sternocleidomaster, we can see it is coming out here. It comes in the lateral cervical region. This is the remainder of the spinal accessory nerve. It runs on the surface of this muscle here. We can see that also. This is the levator scapulae muscle. It crosses the lateral cervical region. And then it enters into the deep surface of the trapezius. And we can see that here. The course of the spinal accessory is very precise. It emerges from the posterior part of the sternocleidomaster at the junction of the upper one third and the lower two thirds. And then as it crosses over to the lateral cervical region, it enters into the deep surface of the trapezius at the junction of the lower one third and the upper two thirds. So this is the course of the spinal accessory nerve. The spinal accessory nerve can be endured in the lateral cervical region when we are doing any surgery for removing of lymph nodes or any concerted trauma. In which case there will be paralysis of the trapezius. A person will have difficulty elevating his shoulder and he will have difficulty shrugging his shoulder, but he will be able to weakly lift up his shoulder by virtue of the levator scapulae muscle and the upper fibers of the serratus anterior. This is the spinal accessory now C11. Now let's take a look at the next nerve which comes in our view. This nerve here. This is the vagus nerve, a very large nerve. This also emerges through the jugular foramen. It runs in the posterior aspect of the carotid sheath. This is the carotid artery. This is the internal jugular vein. It runs in the posterior aspect. We have completely removed it and it runs down. And as it is running down it gives pharyngeal branches, which we cannot see here, but we can see this branch which is coming from the vagus. This is the superior laryngeal nerve and we can see it clearly dividing into two branches, this one and this one. The superior laryngeal nerve divides into internal laryngeal which pierces through the thyroid membrane and supplies sensation to the upper part of the larynx, above the vocal cord. And the external laryngeal nerve it continues down and it supplies the cricothyroid muscle. This external laryngeal nerve is accompanied by the superior thyroid artery. Therefore when we are doing thyroid surgery we are likely to injure, unless we are careful, we are likely to injure the external laryngeal nerve. So external laryngeal nerve and internal laryngeal nerves are divisions of the superior laryngeal nerve. This is the branch of the vagus and we can clearly see it here. The vagus nerve will then cross in front of the subclavian artery and it will give branches at the root of the neck of the laryngeal nerve which we shall see in a later dissection. So that's about the vagus. The third nerve that comes to our view is this one here. This is the hypoglossal nerve. This comes out through the hypoglossal canal and we can clearly see it is crossing as a loop in front of the bifurcation of the common carotid into internal and external carotid arteries. So this is the course of the hypoglossal nerve and then it accompanies the lingual artery and it enters into the tongue. The lingual artery goes deep to the hypoglossal nerve. The hypoglossal nerve goes superficially to the hypoglossal nerve when they enter into the tongue. We can see this nerve coming out from the hypoglossal nerve. This is actually not a part of the hypoglossal. This is a part of the cervical plexus, the ancestral cervicalis, the superior limb of ancestral cervicalis which came from the loop of C1, C2. This travels with the hypoglossal nerve and some of the fibres they go down and from the loop of ancestral cervicalis the hypoglossal they supply the geniohyoid and the thyrohyoid. So that is what we see here. This is the hypoglossal nerve. The next nerve that you can see, we can see only a little bit of it. Now I am very close to the intratemporal fossa. We can see these two muscles coming out from the styloid process. This is the styloid process. This is the styloglossus muscle and this is the styloferringes muscle. The styloferringes muscle it enters into the pharynx between the superior and the middle pharyngeal constrictors. This is the superior pharyngeal constrictor below is the middle. And accompanying the styloferringes we can see this nerve here. This is the glossopharyngeal nerve. The glossopharyngeal nerve accompanies the styloferringes and it enters into the pharynx. Glossopharyngeal nerve supplies only one muscle of the pharynx and that is this muscle, the styloferringes. Thereafter the glossopharyngeal nerve divides into a plexus which supplies the pharyngeal plexus and it enters into the pharyngeal nerve. So, therefore, we have seen the lower pharyngeal nerves. We have seen CN11. We have seen CN10. We have seen CN12. And we have seen CN9. So, these are the points which I wanted to show you about the lower pharyngeal nerves on the right side. Thank you very much for watching. Dr. Sanjay Sanyal signing out. Solomon is the camera person. Like and subscribe.