Blood

• Blood components


  • Red blood cells
  • White blood cells
  • Platelets
• Red blood cells


  • Carry oxygen from the lungs to all cells in the body
  • Have a concave disc shape , which gives them a large surface area for absorbing oxygen
  • Have no nucleus, allows more room for carrying oxygen
  • Contain the red pigment haemoglobin which binds to oxygen in the lungs and releases it in the body tissues
• White blood cells


  • Defend against infection
  • Some change shape to gobble up unwanted microorganisms (phagocytosis)
  • Others produce antibodies to fight microorganisms
  • Also release antitoxins to neutralise toxins made by microorganisms
  • Have a nucleus
• Platelets


  • Help blood clot
  • Small cell fragments without a nucleus
  • Help stop bleeding and prevent microorganisms from getting in
• Plasma


  • The liquid part of blood that carries everything
  • Pale straw-coloured liquid
  • Carries nutrients, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins