the circulatory system

• What is the heart?

  An organ that pumps blood around the body, using chambers called the ventricles.
• What are valves?

  Structures that prevent the backflow of blood.
• What are peacemakers - biological?

  A group of cells that control heart rate.
• How does the double circulatory system work?

  • Gas exchange takes place in the lungs.
  • The left ventricle contracts to pump blood around the rest of the body.
  • The right ventricle pumps blood to the lungs.