Final answer:
The valve between the right ventricle and the pulmonary artery is called the pulmonary valve or pulmonary semilunar valve, and it prevents backflow of blood during ventricular relaxation.
Step-by-step explanation:
The valve between the right ventricle and the pulmonary artery is called the pulmonary valve, also known as the pulmonary semilunar valve, the pulmonic valve, or the right semilunar valve. This valve has three small flaps made of endothelium reinforced with connective tissue. Its function is to prevent the backflow of blood into the right ventricle during ventricular diastole. The pulmonary trunk emerges from the right ventricle and branches off into the left and right pulmonary arteries that transport blood to the lungs for gas exchange.