Final answer:
The heart sends deoxygenated blood to the lungs via the pulmonary trunk, which splits into two pulmonary arteries. After gas exchange in the lungs, four pulmonary veins return oxygenated blood to the heart.
Step-by-step explanation:
The one pulmonary trunk leaves the heart and bifurcates into two pulmonary arteries, while four pulmonary veins return blood to the heart. The vessel responsible for transporting this blood away from the heart is the pulmonary trunk, which exits the right ventricle and eventually splits into the left and right pulmonary arteries, facilitating blood flow to each lung.
Within the lungs, the blood travels through smaller arteries and arterioles, reaching the pulmonary capillaries where gas exchange occurs at the alveoli. After becoming oxygenated, the blood enters pulmonary venules and then the pulmonary veins. Finally, four pulmonary veins, comprising two from each lung, return the oxygen-rich blood to the left atrium of the heart.