The blood from the body tissues arrives at the heart in vessels called the inferior and superior Vena Cavas. It enters the right atrium of the heart and is pumped passed the tricuspid valve into the right ventricle. Then a second, delayed contraction, pushes the blood through another valve, the pulmonary semilunar valve into the pulmonary trunk. From here the blood moves through the left and right pulmonary arteries and enters the left and right lungs where gas exchange takes place. Carbon dioxide is dropped off and oxygen is picked up by the hemoglobin of the blood by a process known as diffusion. Then oxygenated blood moves through the pulmonary veins to the heart and enter into the left atrium. This completes the pulmonary circuit of the cardiovascular system.
pulmonary veins
Blood entering the right atrium is deoxygenated and saturated with CO2. Blood that is entering the left atrium has passed through the lungs and is oxygenated. It returns to the left atrium via the pulmonary vein and is saturated with oxygen. - Med Student
Four main blood vessels enter/exit the heart: two veins and two arteries. Oxygenated blood enters the left ventricle through the pulmonary vein. This same blood is then pumped out of the left atrium via the aorta. Meanwhile, de-oxygenated blood enters the heart in the vena cava; before leaving through the pulmonary artery.
There are no vessels that drain the right atrium, except, perhaps the coronary veins. The right atrium moves blood through the tricuspid valve into the right ventricle of the heart.
The right atrium (upper chamber) and the right ventricle (lower chamber)
The Pulmonary Artery which takes the deoxygenated blood to the lungs.
Superior and inferior Vena Cava
deoxygenated blood
The blood enters through the superior and inferior vena cava.
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Two, the left and right pulmonary veins.
the liver