The blood

• Blood is a tissue with red blood cells , white blood cells and platelets suspended in plasma.
• Plasma

  Blood plasma is a yellow liquid - it transports cells and platelets around the body through the blood vessels. It also transports dissolved substances including:

  • Carbon dioxide from respiring cells
  • Soluble products of digestion such as glucose and amino acids
  • Urea - a waste product formed when the liver breaks down excess proteins
• Red blood cells

  Most of the cells in the blood are red blood cells . These cells transport oxygen around the body through the blood vessels.

  They have several adaptations for this function including :

  • Contains haemoglobin - red pigment which binds reversibly to oxygen
  • No nucleus - provides more space to contain more haemoglobin
  • Biconcave ( disc shape ) - increases surface area to volume ratio for diffusion
• What are the red blood cell adaptions ?

  They have several adaptations including :

  • Contains haemoglobin - red pigment which binds reversibly to oxygen.
  • No nucleus - provides more space to contain more haemoglobin.
  • Biconcave ( disc shape ) - increases surface area to volume ratio for diffusion.
• White blood cells

  White blood cells are larger than red blood cells and have a nucleus.

  They are part of the body's immune system. There are different types of white blood cells including :

  • Phagocytes - engulf and destroy
  • Pathogens - disease causing organisms
  • Lymphocytes - produce antibodies , proteins that bind to pathogens and lead to their destruction.
• What are the 3 types of white blood cells?

  lymphocytes , phagocytes and pathogens
• Platelets

  Platelets are fragments of cells with no nucleus.

  They are involved in forming a blood clot at a cut or in a wound. Platelets are trapped when a meshwork of fibrin protein forms
• In the blood there is :

  55 % plasma

  <1 % white blood cells and platelets

  45 % red blood cells