What is Circulatory System
The human body’s complex network of blood vessels is powered by a central pump—the heart . Blood is pumped out through the aorta into all the major arteries. These subdivide into arterioles and capillaries, through the walls of which nutrients pass into tissues or organs. Contractions of the heart muscle pump blood along the arteries. Blood flow along veins is assisted by the contraction of muscles in the limbs. Valves prevent it from flowing backward. Many of the diseases of the cardiovascular system arise either from the constriction (angina) or blockage (stroke) of blood vessels, from malfunctioning valves, or from problems with the pumping action of the heart (palpitations).Capillaries collect the waste products of metabolism, such as carbon dioxide, and drain into venules and veins, which carry blood back to the heart and lungs. The portal system connects the small intestine to the liver. Nutrient-rich blood is carried by the portal vein from the digestive organs to the liver, where nutrients are absorbed for processing or stored until they are needed.


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