The pulmonary trunk is a major vessel of the human heart that originates from the right ventricle. It branches into the right and left pulmonary arteries, which lead to the lungs. Each of these vessels has elastic walls similar to those of the aorta, though somewhat thinner, and they are considered to be arteries even though the blood they carry is not oxygenated. The trunk itself is relatively short and wide. The function of these vessels is to transmit oxygen-depleted, carbon dioxide-rich blood from the right ventricle to the lungs. In the lungs, the blood becomes purified and oxygenated again. It then travels back to the left side of the heart to be distributed throughout the body. The right ventricle must first pump the blood to force it through the pulmonary valve and into the pulmonary trunk, which is the only outlet from the right ventricle. From here, the blood travels through each of the pulmonary arteries to reach the corresponding lungs.