(3.16)

In this section we'll look at the arteries and veins of the head and neck. First we'll look at the two major arteries that supply the region. Then we'll look at the blood vessels inside the cranial cavity, then at the ones outside it.

On each side two major arteries, the common carotid and the subclavian, emerge through the opening at the top of the chest, the superior thoracic aperture. To see them we'll look look at a dissection in which we've already removed the overlying structures: the sternocleidomastoid muscle, the infrahyoid muscles, and the internal jugular vein. Here's the clavicle, the first rib is here.

This is the anterior scalene muscle. Here's the trachea, here's the thyroid gland. Here are the common carotid and subclavian arteries, coming up through the superior thoracic aperture. As seen in Tape 3, these arise from the arch of the aorta, the two on the left directly, the two on the right indirectly from the brachiocephalic artery. We'll look at the subclavian artery first.

On each side the subclavian artery passes upward and laterally, giving off these branches which we'll see in a moment. It then passes behind this muscle, the anterior scalene, crossing the underlying first rib as it does so. Emerging here, it runs down beneath the clavicle towards the axilla to supply the upper extremity.

The branches that arise from the subclavian artery in the base of the neck are the internal thoracic, the thyro-cervical trunk, which we'll remove, and this important branch, the vertebral artery, which we'll come back to shortly.

We'll leave the subclavian artery for now, and follow the common carotid artery. The common carotid artery runs upward lateral to the thyroid gland, the trachea and the larynx. A little below the level of the angle of the mandible, which is here, the common carotid divides into the external, and internal carotid arteries.

To see these more clearly we'll take the parotid gland, and the ramus of the mandible out of the picture. At the bifurcation of the common carotid, which is better seen in this more typical specimen, there's a widening, the carotid sinus. Usually the internal carotid artery runs almost straight upward, but in this dissection, the one we'll be following, it takes quite a forward curve.

The branches of the external carotid arteries supply the skull, the dura, and all of the head outside the cranial cavity, apart from the orbit. The brain is supplied by the internal carotid arteries and the vertebral arteries. We'll move on now, to follow those arteries into the cranium, and look at their branches.