Circulatory System: General Structure (Edexcel IGCSE Science (Double Award): Biology): Revision Note

Exam code: 4SD0

Circulatory System

  • The circulatory system is a closed network of blood vessels connected to the heart, with blood flowing in one direction

  • Arteries carry blood away from the heart to organs, and this blood is usually oxygenated

    • The pulmonary artery is an exception, it carries deoxygenated blood away from the heart

  • Arteries branch into narrower arterioles and then capillaries within the organs

  • In the organs, respiring cells use up the oxygen from the blood

  • Capillaries join to form venules, which widen into veins carrying blood back to the heart, and this blood is usually deoxygenated

    • The pulmonary vein is an exception, it carries oxygenated blood to the heart

  • A different network of lymphatic vessels collect all the excess tissue fluid that leaks out of the capillaries and delivers it back to the circulatory system

Diagram of the circulatory system showing blood flow between the heart, lungs, liver, gut, kidneys, and other organs with labelled veins and arteries.

The circulatory system

Main Blood Vessels of the Circulatory System Table

Organ

Towards organ 

Away from organ

Heart

Vena cava, pulmonary vein

Aorta, pulmonary artery

Lung

Pulmonary artery

Pulmonary vein

Liver

Hepatic artery and hepatic portal vein

Hepatic vein

Kidney

Renal artery

Renal vein


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