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

• The circulatory system consists of a closed network of blood vessels connected to the heart
  • Oxygenated blood is carried away from the heart and towards organs in arteries
  • These narrow to arterioles and then capillaries as they pass through the organ
  • In the organs, respiring cells use up the oxygen from the blood
  • The capillaries widen to venules and finally veins as they move away from the organs
  • Veins carry deoxygenated blood back towards 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