Circulatory System : This system comprises of the heart, blood vessels (arteries, veins, capillaries).
The Complex network of tubes called blood vessels, (which extends as a network, throughout the body) together with the blood they contain and the heart, make up the Circulatory System.
It is called Circulatory System, because it circulates or moves the blood around from the heart to the body's tissues and organs and back to the heart again, ready for its next journey. The entire circuit is completed in the body, as in a circle. Hence, the word is circulation.
There are 3 main types of blood vessels in the body:
• Arteries : Arteries are elastic tubes that carry the blood from heart to different parts of the body. Generally they carry oxygenated or pure blood except pulmonary artery, which carries oxygen poor blood.
• Veins : Veins carry the blood from different parts of the body towards heart. Generally they carry oxygen poor blood or deoxygenated blood except for pulmonary vein, which carries oxygen rich blood. These are less elastic.
• Capillaries : Capillaries are the smallest blood vessels and they are the link between the arteries and the veins.
The blood is pumped throughout the body by a hollow muscular organ called heart, which is the chief organ of Circulatory System.