A student of anatomy should have a clear picture of the blood flow to and from the body. Blood enters into the right atrium of the heart from the body. From the right atrium it travels through the right atrioventricular valve (tricuspid valve) to the right ventricle. The right ventricle pumps it out through the pulmonary valve into the pulmonary artery and then to the lungs. There it picks up oxygen and returns to the left atrium of the heart through paired pulmonary veins on each side. From the left atrium, blood passes through the left atrioventricular valve (bicuspid or mitral valve) to the left ventricle, and the left ventricle pumps it out through the aortic valve into the aorta. From the aorta, the blood flows through the thorax and abdomen. In the pelvis the aorta ends as paired common iliac arteries. The common iliacs split into internal and external iliac arteries. The internal iliacs mainly supply the pelvis and nearby areas, while the external iliacs continue as femoral arteries down into the leg. Internal, external, and common iliac veins bring blood back from those regions until it reaches the abdomen, where the veins become the inferior vena cava, which returns blood to the right atrium.
Within the head and neck are many blood vessels, each with numerous branches. In this chapter we will concentrate on those vessels that supply and drain the teeth and oral cavity, starting with the heart and tracing the blood into the head and neck and then back to the heart again.
The pathways to the right and left sides of the head and neck are slightly different. On the right side, the brachiocephalic artery (brachio meaning “arm”; cephalic meaning “head”) branches off the arch of the aorta. Coming off the brachiocephalic artery are the right subclavian artery to the right arm, and the right common carotid artery to the right side of the head. The left common carotid artery comes directly off the arch of the aorta on the left side, and the left subclavian artery comes off the arch of the aorta lateral to the left common carotid artery.
In the neck on both sides, the common carotid artery runs within the carotid sheath, along with the internal jugular vein and the vagus nerve, and lies beneath the sternocleidomastoid muscle, which runs along the side of the neck. At about the level of the larynx, the common carotid divides into the external carotid and the internal carotid arteries.
The internal carotid artery has no branches in the neck but goes up to enter the skull. Once inside the skull, it branches to supply the eyes, the brain, and some limited regions of the coverings of the brain (Fig. 32-1).
Unlike the internal carotid artery, the external carotid artery has a number of branches in the neck, as shown in Figs. 32-1 and 32-2. The best way to study these arteries are by the directions and orders in which they come off of the external carotid artery.
Anterior branches: There are three anterior branches. In order of lowest to highest, they are (1) the superior thyroid artery to the thyroid gland and larynx; (2) the lingual artery to the tongue and floor of mouth; and (3) the facial artery that supplies the submandibular salivary gland, the area beneath the chin, and the face.
The lingual artery branches off the external carotid artery below the facial artery. The lingual artery then travels forward and deep, going beneath the hyoglossus muscle of the tongue and ending in three branches: the dorsal lingual artery to the deep posterior part of the tongue, the deep lingual artery to the deep anterior part of the tongue, and the sublingual artery to the ventral surface of tongue and floor of the mouth. The lingual artery supplies the tongue and the tissue in the floor of the oral cavity. If you have ever cut your tongue, you know that there is a well-developed blood supply within this tissue, which is completely supplied by the lingual artery (Fig. 32-3). Quite frequently the lingual and facial arteries come off the external carotid as one branch and then split. This branch is referred to as the linguofacial trunk.