The answer is a <span>fulcrum</span>
body language, has he been acting weird? Agreeing or disagreeing in a joking way, lot of eye contact, complements you, the way he responds to touch (like a hand on his shoulder, holding his hand, ect.), and does he lean forward when your speaking to him despite already sitting close
Superior/inferior vena cava - right atrium - right ventricle - pulmonary artery - lungs(for oxygenation) - pulmonary vein