Blood

• Blood


  • A tissue
  • Runs through veins and arteries
  • Supplies cells with oxygen and dissolved food
  • Contains fluid plasma which contains red blood cells, white blood cells, and platelets
• Plasma


  • Straw coloured fluid
  • 55% of the total blood fluid volume
  • Majority of plasma is made of water
  • Reminder is made up of hormones, products of food digestion from the small intestine and the waste byproducts of cell metabolism eg urea
  • Transports CO2 by product of respiration and alters the pH of the plasma
  • pH alkaline stays between 7.35 and 7.45
• Why is blood red?

  • Due to the presence of red blood cells
• Red blood cells


  • Transports oxygen from lungs to cells
  • Biconcave in shape to increase the surface area for oxygen
  • Doesn't have a nucleus
  • 6-8 micrometres in diameter
  • 10x smaller than a human egg cell
  • Their size and shape allows them to travel through veins and arteries easy without getting stuck
  • Some genetic disorders such as sickle cell anaemia causes changes to the shape of the red blood cell causing them to get stuck in veins
• Haemoglobin


  • Pigment inside a red blood cell
  • When combined with oxygen it becomes oxyhaemoglobin which has a bright red colour
  • Helps oxygenate deoxygenated blood
• White blood cells


  • A group of cells that form the body's defence system against microorganisms
  • Unusual shaped nucleus
  • Nucleus is often multi-lobed
• Platelets


  • Remains of a giant cell formed in the bone marrow called the megakaryocyte
  • No nucleus
  • Involved in the blood clotting process
  • Prevents extreme blood loss