You might want to consider looking up your question word for word. I got a good result from Google that you could play off of. This is what it said:
Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. As the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.
Right now, I'm unable to write something myself, but later if you still need it answered, I'll see what I can do.
