Lymphocytes

• Blood is a tissue. One of its jobs is to act as a huge transport system.
• Main things in blood

  • Red Blood Cells
  • White Blood Cells
  • Platelets
  • Plasma
• Red Blood Cells


  • Carry Oxygen from the lungs to all the cells in the body
  • Have a biconcave disc shape to give a large surface area for absorbing oxygen
  • Don't have a nucleus to allow more room to carry oxygen
  • Contain haemoglobin, a red pigment that contains Iron
• Oxygen transport by red blood cells

  1. In the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin

  2. In body tissues, oxyhaemoglobin splits up into haemoglobin and oxygen, to release oxygen to the cells
• White Blood Cells


  • Defend against infection
  • Phagocytes can change shape to engulf unwelcome microorganisms
  • Lymphocytes produce antibodies and antitoxins against microorganisms
• When you have an infection

  Your white blood cells multiply to fight it off
• Platelets


  • Help the blood to clot at a wound to stop bleeding and prevent microorganisms getting in
  • Lack of platelets can cause excessive bleeding and bruising
• Plasma


  The pale straw-coloured liquid in blood that carries everything including red and white blood cells, platelets, nutrients, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins
• Blood tests can be used to diagnose loads of things because the blood transports so many chemicals produced by so many organs and it's easier to take blood than a piece of muscle
• Central nervous system