It is made up of two separate circuits and blood passes through the heart twice. The pulmonary circuit carries blood to the lungs where carbon dioxide is removed from the blood and oxygen is absorbed by hemoglobin in the red blood cells and then back to the left side of the heart. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original EssayThe systemic circuit carries blood throughout the body to supply oxygen and returns the material of life and deoxygenated blood, blood that contains carbon dioxide, to the heart on the right side. The tricuspid valve and pulmonary valve on the right side of the heart, and the mitral valve and aortic valve on the left side act like doors that open and close, to make sure blood travels in one direction through the heart. The upper part of the heart connects to the large blood vessels of the body, the aorta on the left side which carries oxygenated blood to the body, the vena cava which carries deoxygenated blood to the lungs, and the pulmonary trunk which originates from the right side and then it branches into the right and left pulmonary arteries which then connect to the lungs, transport poorly oxygenated blood to the lungs and the pulmonary veins transfer oxygenated blood from the lungs to the heart. The heart pumps blood which contains digested food, water, red blood cells which carry oxygen from the lungs, hormones from various glands, heat energy, white blood cells and antibodies, from the left side, through the aorta, l main artery of the heart, in the arteries. Blood travels through arteries, into smaller branches of blood vessels, the capillaries. Through this network of capillaries, the blood reaches every part of your body to supply all the necessary nutrients to the cell and carry the vital product of cellular respiration through the veins. The blood is deoxygenated, then returns to the heart through your veins. The branches of the veins join together to form larger veins, which run up the right side of the heart through the vena cava. Please note: this is just an example. Get a custom paper from our expert writers now. Get a Custom EssayThen the heart pumps deoxygenated blood to the lungs. As the heart relaxes between each contraction, blood from the veins fills the right side of the heart. At the same time, blood receiving oxygen from the lungs fills the left side ready to enter the aorta and start the whole process again.