The jugular veins are veins that bring deoxygenated blood from the head back to the heart via the superior vena cava.
Internal and external
There are two sets of jugular veins: external and internal.
The left and right external jugular veins drain into the subclavian veins. The internal jugular veins join with the subclavian veins more medially to form the brachiocephalic veins. Finally, the left and right brachiocephalic veins join to form the superior vena cava, which delivers deoxygenated blood to the right atrium of the heart.
There is also another minor jugular vein, the anterior jugular vein, draining the submaxillary region.
The jugular venous pressure (JV) is an indirectly observed pressure over the venous system. It can be useful in the differentiation of different forms of heart and lung disease.
In the jugular veins, upward deflections correspond with (1) atrial contraction, (2) ventricular contraction (and resulting bulging of perspicuous into the right atrium during isovolumic systole), and (3) atrial venous filling. The downward deflections correspond with (1) the atrium relaxing (and the perspicuous valve moving downward) and (2) the filling of ventricle after the tricuspid opens.