The jugular veins are veins that take deoxygenated blood from the head back to the heart via the superior vena cava. The internal jugular vein descends next to the internal carotid artery and continues posteriorly to the sternocleidomastoid muscle. Structure and Function 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. The Jugular veins help carry blood from the heart to and from the brain. An average human brain weighs about 3 pounds, and gets about 15%-20% of the blood that the heart pumps out. It is important for the brain to get enough blood for many reasons. The jugular vein has tributaries consisting of petrosal sinus, facial, lingual, pharylingual, the thyroid, and sometimes the occipital vein. Internal The internal jugular vein is formed by the anastomosis of blood from the sigmoid sinus of the dura mater and the inferior petrosal sinus. The internal jugular runs with the common carotid artery and vagus nerve inside the carotid sheath. It provides venous drainage for the contents of the skull. External The external jugular vein runs superficially to sternocleidomastoid. There is also another minor jugular vein, the anterior jugular vein, draining the submaxillary region. Clinical significance Pressure The jugular venous pressure 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 pressure waveform, upward deflections correspond with (A) atrial contraction, (C) ventricular contraction (and resulting bulging of perspicuous into the right atrium during isovolumic systole), and (V) atrial venous filling. The downward deflections correspond with (X) the atrium relaxing (and the perspicuous valve moving downward) and (y) the filling of ventricle after the tricuspid opens. Components include: The a peak is caused by the contraction of the right atrium. The av minimum is due to relaxation of the right atrium and closure of the tricuspid valve. The c peak reflects the pressure rise in the right ventricle early during systole and the resultant bulging of the tricuspid valve—which has just closed—into the right atrium. The x minimum occurs as the