Circulatory System: General Structure (Edexcel IGCSE Biology): Revision Note
Exam code: 4BI1
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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
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 artery | Hepatic vein |
Kidney | Renal artery | Renal vein |
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