Superior and Inferior Vena Cava Anatomy

• The superior and inferior vena cava are major blood vessels, which return deoxygenated blood to the heart.
• The superior vena cava returns deoxygenated blood from the head, neck, arms, and chest.
• The inferior vena cava returns blood to the heart from the abdomen, pelvis, legs, and feet.
• Both vessels return blood at the right atrium.
• The superior vena cava meets this heart chamber from above.
• The inferior vena cava joins it from a posterior and inferior position.

Superior Vena Cava

• Originates at the junction of the right and left brachiocephalic veins
• Travels down toward the heart vertically.
• Lies anterior to the spine, posterior to the ribcage, and to the right of both the aorta and the trachea.
• Merges at the right atrium, protected by the pericardium.
• There is no valve located between the superior vena cava and the right atrium of the heart.

Inferior Vena Cava

• Originates at around the L5 vertebrae where the left and right iliac veins converge.
• Travels upward toward the heart.
• Lies anteriorly from the spine and to the right of the descending aorta along the posterior abdominal wall.
• It is longer and has a wider diameter than the superior vena cava.
• Meets the heart at the posterior aspect of the right atrium.
• There is no valve between the inferior vena cava and the right atrium.

Function of the Superior Vena Cava

• Returns deoxygenated blood from the upper portion of the body to the heart.
• Collects blood from brachiocephalic veins, jugular veins, azygos veins, and subclavian veins.
• The blood travels through the short and thin-walled vessel where it joins the heart at the right atrium depositing the deoxygenated blood.
• The blood circulates through the heart to become oxygenated and returns to the tissues.

Function of the Inferior Vena Cava

• Returns deoxygenated blood from the lower portion of the body to the heart.
• Collects blood from the iliac, renal, lumbar, and veins of the reproductive organs, and the hepatic vein.
• These vessels deposit their deoxygenated blood which then moves the blood to the posterior side of the right atrium.
• Once in the heart, the blood then begins its cycle to become re-oxygenated and ultimately cycle through the tissues of the body again.

Middle Cardiac Vein

• Part of the coronary circulation.
• Collects deoxygenated blood from the heart muscle of both the right and left ventricle as well as the ventricular septum tissues.
• Returns it to the coronary sinus.
• Originates at the apex, or the inferior point of the heart.
• Travels superiorly through the posterior longitudinal sulcus.
• Deposits the deoxygenated blood into the coronary sinus of the heart.

Coronary Sinus

• Drains deoxygenated blood from the coronary circulation into the right atrium of the heart.
• Collects deoxygenated blood from the great cardiac vein, the middle cardiac vein, and the left marginal vein.
• It does not collect blood from the heart's muscle tissue directly.
• Transports the blood toward the posterior aspect of the right atrium where it deposits the deoxygenated blood.
• Located on the backside of the heart, positioned almost horizontally, and wraps around the posterior side of the coronary sulcus.
• Its length can vary widely among people.