blood

• red blood cells transport oxygen
• white blood cells defend against disease
• platelets are for clotting to seal wounds
• plasma is for transport
• oxygen + haemogoblin = oxyhaemogoblin
• the two functions of blood in the body are transport and immunity
• Red blood cells

  • no nucleus - more room to carry oxygen
  • Bioncave disc shape - increases surface area so there is more membrane for oxygen to diffuse through
  • Cytoplasm containing haemoglobin for transport of oxygen
• Red and White blood cells

  • White blood cell is bigger compared to red blood cell
  • White blood cell has no fixed shape because it is flexible while a red blood cell has a bioncave disc shape
  • White blood cell is a three lobed nucleus while a red blood cell has no nucleus
• Phagocytes engulf other cells especially bacteria, they digest and destroy them-

  Cytoplasm 'arms' engulf bacteria and then the bacteria trapped in the phagosome is digested by enzymes

  
• Plasma is the liquid part of the blood (pale yellow in colour) it carries dissolved substances around the body such as :

  • CO2 - from body cells to lungs where it is exhaled
  • Soluble Nutrients - e.g glucose from small intestine to all body cells
  • Urea - waste product made in liver to the kidneys to be excreted
  • Hormones - from glands in the body to where they are needed
  • Distributes heat
• Blood clotting is important because it prevents us from losing blood from the blood vessels, and it also prevents pathogens from entering the blood, which could cause infection.