(3.29)

Let's move on now, to look at the blood supply of the head and neck outside the cranial cavity. We'll look first at branches of the subclavian artery that make a contribution, then at the external carotid artery and its branches.

Here's the subclavian artery again. Here's the vertebral artery which we've seen already. Arising here in front of it is the thyro-cervical trunk, a short vessel that immediately divides, giving off these branches to the shoulder region, and the inferior thyroid artery.

The inferior thyroid artery gives off this small ascending cervical artery, then runs medially, deep to the common carotid artery, to reach the lower pole of the thyroid gland.

Now we'll go to a different dissection, to look at the external carotid artery and its branches. We've removed the sternocleidomastoid muscle, the internal jugular vein, and the parotid gland. Here's the common carotid artery, dividing into the internal carotid, and the external carotid.

The external carotid artery runs upward, passing beneath the posterior belly of the digastric muscle, and the stylohyoid muscle. It ends above the stylohyoid by dividing into its two terminal branches, which we'll see in a minute.

The first branch of the external carotid is the superior thyroid artery. It runs downwards alongside the larynx, to reach the upper pole of the thyroid gland.

The next branch is the lingual artery. It runs downwards and forwards, passing deep to the hyoglossus muscle, to supply the tongue. To see the remaining branches of the external carotid, we'll remove the posterior belly of the digastric, and the stylohyoid muscle.

This is the facial artery. The facial artery runs forwards, passing between the submandibular gland and the angle of the mandible, and emerging here. The facial artery crosses the mandible (it's extremely tortuous in this specimen) and runs upwards and forwards, branching to supply the lower part of the face.

Here, arising posteriorly, is the occipital artery. The occipital artery runs steeply upwards, then passes deep to the digastric and splenius muscles. It re-emerges here and runs upwards, branching to supply the posterior part of the scalp.

Also arising posteriorly up here is the smaller posterior auricular artery. It runs more superficially to supply the scalp behind the ear.

We'll remove these two posterior branches to see one more branch that arises deeply, the ascending pharyngeal. It passes upwards deep to the external carotid to supply the upper part of the pharynx.