4.8.14 Sympathetic trunk, cervical plexus



To end this section we'll look at the one part of the autonomic system that is clearly visible: the sympathetic trunk. We'll also look briefly at the cervical nerves.

To see the sympathetic trunk, we've removed all the cranial nerves, and the internal jugular vein. We'll also move the common and internal carotid arteries aside. Here's the cervical sympathetic trunk. It runs up the neck on the fascia that lies in front of the longus muscles.

This massive thickening at the top of the sympathetic trunk is the superior cervical ganglion. From its upper end this nerve, the internal carotid nerve arises, and joins the internal carotid artery as it enters the carotid canal.

Now we'll move on to look at the cervical plexus. To see it, we'll look at a dissection in which only the sternocleidomastoid muscle has been removed.

Here's the cervical plexus. It's formed from the anterior roots of C1, 2, 3 and 4. These emerge in front of the middle scalene muscle. Most of the branches of the plexus run laterally, this one runs straight downward: its the phrenic nerve.

The phrenic nerve runs downwards into the thorax on the front of the anterior scalene muscle, to innervate the diaphragm.

Many of the branches of the cervical plexus emerge here, around the posterior border of the sternocleidomastoid muscle. These are the supraclavicular nerves, which pass downward and laterally to supply the upper chest and shoulder region.

This is the great auricular nerve, which supplies this area on the side of the face. This is the posterior auricular, which supplies this area.

Here just beneath the sternocleidomastoid is the lesser occipital nerve. Here more posteriorly, is the greater occipital nerve, arising from the posterior root of C2. The occipital nerves supply this area on the back of the scalp.

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