Venae cavae
The superior and inferior vena cava are collectively called the venae cavae. They are the vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

s that return deoxygenated blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 from the body into the heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

. They both empty into the right atrium
Right atrium
The right atrium is one of four chambers in the hearts of mammals and archosaurs...


The inferior vena cava
Inferior vena cava
The inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....

 (or caudal vena cava in animals) travels up alongside the abdominal aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...

 with blood from the lower part of the body (see # 11 in the diagram). It is the largest vein in the body.

The superior vena cava
Superior vena cava
The superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...

 (or cranial vena cava in animals) is above the heart, and forms from a convergence of the left and right brachiocephalic vein
Brachiocephalic vein
The left and right brachiocephalic veins in the upper chest are formed by the union of each corresponding internal jugular vein and subclavian vein...

s that contain blood from the head and the arms (see # 3 in the diagram).
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