The heart consists of four chambers, four one-way valves, and a set of arteries and veins that regulate the normal flow of blood within the body.
The smooth functioning of the circulatory system is maintained by a complex network of blood vessels that circulate blood throughout the body and back to the heart. Whereas veins bring deoxygenated blood back into the heart, those that carry oxygenated blood away from the heart to other tissues in the body are known as arteries. The two exceptions to these are the pulmonary arteries and pulmonary veins, as well as the umbilical artery and vein.
The heart’s two upper chambers are called the atria, with the atrial septum dividing the right and left atria. The superior and inferior vena cava are major veins that supply the right atrium with deoxygenated blood from the rest of the body.
The superior vena cava brings deoxygenated blood into the right atrium from the upper limbs and head, whereas deoxygenated blood from the lower abdomen and limbs is brought into the heart through the inferior vena cava.
The pulmonary veins supply oxygenated blood from the lungs into the left atrium and are the only veins in the body to carry oxygenated blood. However, during pregnancy, the umbilical vein carries oxygenated and nutrient-rich blood from the placenta to the fetus.
Both atria contract and release blood into the ventricles when full, a process controlled by the atrioventricular valves. The flow of deoxygenated blood from the