(PhysOrg.com) -- Water vapor and clouds are the major contributors to Earth's greenhouse effect, but a new atmosphere-ocean climate modeling study shows that the planet's temperature ultimately depends on the atmospheric level of carbon dioxide.
Deoxygenated blood enters the right atrium through three major veins: the superior and inferior vena cava and the coronary sinus. The superior vena cava returns all of the blood to the heart from tissues superior to the heart in the head, neck, arms and upper thorax.Likewise, the inferior vena cava returns blood to the heart from tissues inferior to the heart, including the legs, abdomen and lower thorax.he right atrium is one of the two atria of the heart, which function as receiving chambers for blood entering the heart. It is located to the right of the left atrium and superior to the much larger and more muscular right ventricle.
Vena cava: The superior vena cava is the large vein which returns blood to the heart from the head, neck and both upper limbs.The inferior vena cava returns blood to the heart from the lower part of the body.The return of blood via the vena cava can be compromised and cause disease.For example, in the superior vena cava syndrome, the symptoms that result from compression of the large vein that carries blood down to the heart.he return of blood via the vena cava can be compromised and cause disease. For example, in the superior vena cava syndrome, the symptoms that result from compression of the large vein that carries blood down to the heart.