The cardiovascular system consists of a network of arteries and veins, the blood that circulates through them, and the heart, which pumps the blood to every body tissue and organ through the arteries and arterioles. Its function is to sustain life, keeping all the tissue cells and organs alive by providing them with oxygen and nutrients. Oxygen is picked up by the red blood cells in the lung alveoli and the nutrients are absorbed from the small intestine, traveling to the liver through the superior mesenteric and portal vein.
Heart
The heart is the hub of the cardiovascular system. It is a muscular organ which contains four cavities: two atria and two ventricles. It is divided into two halves; the right side and the left side. The right half is composed of the right atrium and the right ventricle, which are connected through the tricuspid valve; running through the cava vein, oxygen-poor blood flows into the right atrium, from which it pours into the right ventricle. Both cavities of the right side are not communicated with those of the left side. Flowing from the lungs through the pulmonary veins, oxygen-rich blood pours into the left atrium, from which it runs into the left ventricle through the mitral valve. When the heart contracts, both ventricles pumps the blood to the organs, with the right ventricle sending the oxygen-poor blood to the lungs and the left ventricle ejecting oxygen-rich blood to every tissue and organ through the aorta and its arterial branches.
Blood Vessels
Arteries, arterioles, vein, venules, and capillaries make up the network of blood vessels through which the blood carries oxygenated blood and brings deoxygenated blood to and from the body tissues and organs. Arteries and arterioles (tiny arteries) convey oxygen rich blood from the left ventricle to every cells and organs in the body. Veins and venules (tiny veins) returns oxygen-poor blood, containing carbon dioxide (CO2), to the right atrium, to be sent to the lungs where CO2 is exhaled. Meanwhile, capillaries are the smallest blood vessels, constituting the vascular bridge that links up the arteries with the veins.
In the lungs alveoli, venous blood releases the CO2 and then is saturated with oxygen. Then it returns to the left atrium through the pulmonary veins. The pulmonary vein is the only vein in the body that carries oxygenated blood, as it lies between the heart and the lungs, while the pulmonary artery is the only artery of the body which carries venous (deoxygenated) blood.
Below, diagram of cardiovascular system
