The Blood

• There are 4 important parts of the blood:

  • Plasma
  • Red Blood Cells
  • White Blood Cells
  • Platelets
• Plasma is the liquid part of the blood that contains red blood cells, white blood cells and platelets
• The blood plasma transports dissolved substances around the body, including digestion products from the small intestine to other organs, carbon dioxide from the organs to the lungs and the waste-product urea from the liver to the kidneys.
• Red blood cells transport oxygen from the lungs to the body cells. They contain the oxygen-carrying molecule haemoglobin. They are adapted to this function by having no nucleus, and dimples in the centre increasing their surface area so oxygen can diffuse in and out rapidly
• White blood cells form part of the immune system for example by making antibodies. They also contain a nucleus which contains DNA that encodes the instructions needed by white blood cells to do their job.
• Platelets are tiny fragments of cells and their job is to help the blood to clot
• Donated blood has many uses in medicine:

  • Replacement post-injury
  • Platelets extracted from blood to help in clotting
  • Proteins extracted from blood for example antibodies
• Donated blood must be the same type as the patient's otherwise the immune system could reject it, possibly resulting in death. Lots of different diseases can also be transmitted by blood.