The heart and blood vessels

• A: Trachea

  B: Lung

  C: Bronchus

  D: Bronchioles

  E: Alveoli surrounded by capillary network

  
• A: Pulmonary artery

  B: Pulmonary vein

  C: Left atrium

  D: Left ventricle

  E: right ventricle

  F: right atrium

  G: Vena cava

  H: Aorta

  
• Valves: stop blood flowing in the wrong direction, prevent backflow of blood into the heart

  
• Circuits of a double circulatory system

  • Deoxygenated blood is pumped by the heart to the lungs where it gains oxygen and loses carbon dioxide- oxygenated blood flows back to the heart
  • oxygenated blood is pumped by the heart to the rest of the body where it loses oxygen and gains carbon dioxide- deoxygenated blood flows back into the heart.
• Vena cava: carries deoxygenated blood from the body to the heart
• Right ventricle: contracts to pump deoxygenated blood to the lungs, going through the pulmonary artery
• When deoxygenated blood is pumped to the lungs

  • the deoxygenated blood flows through the capillary network around the alveoli and gas exchange happens
  • oxygen diffuses out of the alveoli into the blood
  • carbon dioxide diffuses out of the blood into the alveoli
• Pulmonary vein: carries oxygenated blood from the lungs to the heart
• Left ventricle: contracts to pump oxygenated blood to the body through the aorta
• Coronary artery: supply heart muscle with oxygenated blood
• What controls a person’s resting heart rate?

  • A group of cells in the heart's right atrium act as a pacemaker and control a person's resting heart rate
  • the pacemaker cells generate electrical impulses that cause the heart muscle cells to contract
• An irregular heart rate be corrected with an artificial pacemaker
• Three blood vessels

  • arteries
  • veins
  • capillaries
• Arteries: Carry high pressure blood away from the heart
• Adaptations of arteries

  • Thick muscular walls to withstand high pressure
  • have elastic fibres so they can stretch under pressure then recoil to push blood along
  • have a narrow lumen to maintain a high pressure
• Capillaries: carry blood close to cells so substances can be exchanged
• Adaptations of capillaries

  • Have very thin walls so substances diffuse over a short distance, improving the rate of diffusion
  • they have permeable walls that let substances in and out
• Veins: carry low pressure blood to the heart
• Adaptations of veins

  • Have valves to stop blood flowing in the wrong direction
  • they have a large lumen to allow blood to flow easily