The right ventricle pumps oxygen-poor blood toward the lungs through the pulmonary valve into the main pulmonary artery.  From there, the blood flows through the right and left pulmonary arteries into the lungs.

CONTENT: Division of Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention. IMAGE: By Door en:User:Wapcaplet. - EN Wikipedia (slightly edited by Stanisław Skowron), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=784427