circulatory system

• Double circulatory system


  Made up of two loops that are joined together
• Circulatory system


  1. Heart pumps deoxygenated blood to the lungs to be oxygenated

  2. Blood returns to the heart

  3. Heart pumps oxygenated blood around the rest of the body

  4. Blood returns when deoxygenated
• Blood vessels


  • Adapted for their functions
• Arteries


  • Aorta
  • Pulmonary artery
  • Coronary artery
• Arteries


  Carry blood away from the heart and branch off into capillaries
• Arteries


  • Thick walls made up of elastic fibres and smooth muscle
  • Relatively narrow lumen
• Heart pumps blood


  Arteries expand to allow high pressure blood flow
• Heart is relaxed


  Elastic fibres in arteries contract to maintain high blood pressure
• Capillaries


  Tiny vessels that surround cells and enable them to exchange different substances with the blood
• Capillaries


  • Permeable walls only one cell thick
  • Increases rate of diffusion
• Veins


  Take blood from capillaries back to the heart
• Veins


  • Walls not as thick as arteries
  • Large lumen to allow blood flow at low pressure
  • Valves to prevent backflow