2.2.3 Blood

• Why is the blood a tissue?

  It is a group of cells with a similar structure and function
• List the components of the blood & their functions

  ● Plasma (liquid) - transports dissolved substances eg. glucose,

  urea, CO2, hormones, suspends cells

  ● Red blood cells - transports oxygen from lungs to body cells

  ● White blood cells - part of immune system, destroys pathogens

  ● Platelets (small fragments of cells) - help clot blood at wounds
• How are red blood cells adapted to their function?

  ● Contain haemoglobin → binds to oxygen

  ● Biconcave discs → large surface area for rapid diffusion of oxygen

  ● No nucleus → more space for haemoglobin
• How are white blood cells adapted to their function?

  Can produce antibodies and engulf pathogens (phagocytosis)
• why is this stattement wrong

  “White blood cells fight disease.”

  Too vague - WBCs help destroy microorganisms that cause disease.
• Explain how a very low number of

  blood components in the body can

  cause these symptoms. (6)

  Tiredness

  ● Fewer red blood cells so less haemoglobin

  ● So less oxygen transported around the body

  ● So less aerobic respiration can take place and more anaerobic

  respiration takes place

  ● So less energy released for metabolic processes

  ● Lactic acid produced causes muscle fatigue

  Frequent infections

  ● Fewer white blood cells

  ● So fewer antibodies produced and fewer pathogens killed

  Bleeding

  ● Fewer platelets so blood does not clot as easily