CIE IGCSE Biology

Revision Notes

9.1 Circulation

The Circulatory System

  • The circulatory system is a system of blood vessels with a pump and valves to ensure one-way flow of blood
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Circulation in Different Animals

  • Fish have a two-chambered heart and a single circulation
  • This means that for every one circuit of the body, the blood passes through the heart once

 

The single circulatory system in fish, IGCSE & GCSE Biology revision notesThe single circulatory system in fish

  • Mammals have a four-chambered heart and a double circulation
  • This means that for every one circuit of the body, the blood passes through the heart twice
  • The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs (the pulmonary circulation)
  • The left side of the heart receives oxygenated blood from the lungs and pumps it to the body (the systemic circulation)

 

The double circulatory system in mammals, IGCSE & GCSE Biology revision notesThe double circulatory system in mammals

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Advantages of a Double Circulation

  • Blood travelling through the small capillaries in the lungs loses a lot of pressure that was given to it by the pumping of the heart, meaning it cannot travel as fast
  • By returning the blood to the heart after going through the lungs its pressure can be raised again before sending it to the body, meaning cells can be supplied with the oxygen and glucose they need for respiration faster and more frequently

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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