These vessels in turn branch many times before reaching the pulmonary capillaries where gas exchange occurs: Carbon dioxide exits the blood and oxygen enters.
The pulmonary trunk arteries and their branches are the only arteries in the body that carry relatively deoxygenated blood blue blood. Highly oxygenated blood returning from the pulmonary capillaries in the lungs passes through a series of vessels that join together to form the pulmonary veins —the only veins red in the body that carry highly oxygenated blood.
The pulmonary veins red bring blood into the left atrium which delivers the blood into the left ventricle which in turn pumps oxygenated blood into the aorta and on to the many branches of the systemic circuit.
Eventually, these vessels will lead to the systemic capillaries where exchange with the tissue fluid and cells of the body occurs. In this case, oxygen and nutrients exit the systemic capillaries to be used by the cells in their metabolic processes, and carbon dioxide and waste products will enter the blood.
The blood that has traveled throughout the body is lower in oxygen concentration than when it entered. The superior vena cava and the inferior vena cava return blood to the right atrium.
The blood in the superior and inferior venae cavae flows into the right atrium, which delivers blood into the right ventricle. This is the chamber on the upper right side of the heart.
When the blood enters the right atrium, most of it flows through the foramen ovale into the left atrium. Blood then passes into the left ventricle. This is the lower chamber of the heart. Blood then passes to the aorta. This is the large artery coming from the heart. From the aorta, blood is sent to the heart muscle itself and to the brain and arms. After circulating there, the blood returns to the right atrium of the heart through the superior vena cava.
Very little of this less oxygenated blood mixes with the oxygenated blood. Instead of going back through the foramen ovale, it goes into the right ventricle. This less oxygenated blood is pumped from the right ventricle into the pulmonary artery. A small amount of the blood continues on to the lungs. Most of this blood is shunted through the ductus arteriosus to the descending aorta. This blood then enters the umbilical arteries and flows into the placenta.
In the placenta, carbon dioxide and waste products are released into the mother's circulatory system. Blood is carried through the body in blood vessels, or tubes, called arteries and veins. The process of moving blood through the body is called circulation. Together, the heart and vessels make up the cardiovascular system.
The heart has four chambers two atria and two ventricles. There is a wall septum between the two atria and another wall between the two ventricles. Arteries and veins go into and out of the heart. Arteries carry blood away from the heart and veins carry blood to the heart. The flow of blood through the vessels and chambers of the heart is controlled by valves.
The heart pumps blood to all parts of the body.
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