the blood dep

• All multicellular organisms need a transport system, and in humans that is blood
• Main components of blood

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

  The liquid part of the blood
• Plasma

  • Pale yellow liquid that carries just about everything that needs transporting around the body
  • Red, white blood cells and platelets are suspended in the plasma
  • Carries digested food products, carbon dioxide, urea, hormones, heat energy
• Red blood cells

  Transport oxygen from the lungs to all the cells in the body
• Red blood cells

  • Small and have a biconcave shape to give a larger surface area for absorbing and releasing oxygen
  • The shape allows for faster diffusion of oxygen
  • Contain haemoglobin which reacts with oxygen to form oxyhaemoglobin in the lungs and releases oxygen in tissues
  • Do not have a nucleus in order to free up space for more haemoglobin
  • Small disc shape to fit and flow through capillaries more easily
• White blood cells

  Part of the immune system that deals with pathogens
• Types of white blood cells

  • Lymphocytes
  • Phagocytes
• Phagocytes

  • Have multi-lobed nucleus and granules of digestive enzymes
  • Non-specific, attack anything not meant to be there
  • Carry out phagocytosis - detect chemicals, engulf pathogenic cell, release digestive enzymes to break it down
• Lymphocytes

  • Produce antibodies
  • Every pathogen has unique antigens on its surface
  • When lymphocytes encounter a foreign antigen, they produce specific antibodies that lock onto and mark the invading pathogens for destruction
  • Antibodies flow around the body to mark all similar pathogens
  • Memory cells are produced that can quickly reproduce antibodies if the same antigen enters the body again