circulatory system

• describe heart

  organ to pump blood around body in double circulatory system
• describe double circulatory system

  right ventricle - pumps deoxygenated blood to lungs for gas exchange

  left ventricle - pumps oxygenated blood to rest of body to supply oxygen
• describe pathway of deoxygenated blood

  1. flows into right atrium through vena cava
  2. right atrium contracts and pumps blood to right ventricle
  3. right ventricle contracts and pumps blood into lungs through pulmonary artery
• describe pathway of oxygenated blood

  1. flow into left atrium through pulmonary vein
  2. left atrium contract and pump into left ventricle
  3. left ventricle contract and pump to body through aorta
• describe pacemaker

  group of cells controlling natural resting heart rate in the right atrium
• give types of blood vessels

  arteries, veins and capillaries
• describe function of arteries

  carry blood away from heart at high pressure
• give adaptations of arteries

  narrow lumen, strong elastic walls and thick muscle
• describe function of veins

  carry blood into heart under low pressure
• give adaptations of veins

  large lumen and valves
• describe function of capillaries

  site of gas exchange of oxygen and carbon dioxide
• give adaptations of capillaries

  permeable and one cell thick walls
• describe function of valves

  ensure one direction blood flow and prevent blood back flow
• describe blood

  tissue containing red blood cells, white blood cells and platelets suspended in plasma
• describe function of red blood cells

  supply oxygen to cells in body
• give adaptations of red blood cells

  haemoglobin - binds to oxygen

  no nucleus - more space for oxygen
• describe function of white blood cells

  part of immune system to defend against disease and infection
• give types of white blood cells

  lymphocytes and phagocytes
• describe lymphocyte white blood cells

  produce antibodies - fight pathogens

  produce antitoxins - neutralise pathogen toxins
• describe phagocytes

  engulf and digest pathogens
• describe platelets

  fragments of blood
• describe function of platelets

  clot blood at wounds - prevent blood pour out and pathogens entering
• describe plasma

  liquid component of blood to transport substance
• give substances transported in plasma

  red blood cells, white blood cells, platelets, glucose, amino acids, proteins and hormones