The human circulatory system

• The heart is a muscular organ that pumps blood around the body in a dual circulatory system.
• The right ventricle pumps blood to the lungs,

  where gas exchange takes place. The left

  ventricle pumps blood around the rest of the

  body
• Valves prevent the blood from flowing back from the ventricles to the atria
• Blood vessels associated with the heart include the aorta, vena cava, pulmonary artery, pulmonary vein and coronary arteries.
• Gas exchange takes place in the lungs. Important features of the lungs are the trachea, bronchi, alveoli and the capillary network surrounding the alveoli.
• The alveoli have the specialised surfaces for gas exchange between air and the blood
• The natural resting heart rate is controlled by a group of cells that act as a pacemaker, located in the right atrium. Artificial pacemakers are electrical devices used to correct irregularities in the heart rate.
• The body contains three different types of blood vessel: • arteries • veins • capillaries