The Blood

• Plasma is the liquid part of the blood

  
• In the plasma we find red blood cells

  
• In the plasma we find white blood cells

  
• Platelets are fragments of cells

  
• Plasmas job it is transport dissolved substances around the body
• Blood plasma transports:

  • soluble digestion products (such as glucose) from the small intestine to other organs.
  • Carbon dioxide (produced by aerobic respiration) from the organs to the lungs to be breathed out.
  • The waste-product urea from the liver to the kidneys to be excreted in urine.
• Red blood cells transport oxygen from the lungs to the body cells.
• Red blood cells contain the oxygen-carrying molecule haemoglobin.
• Haemoglobin + oxygen -(lungs)-> oxyhaemoglobin
• oxyhaemoglobin -(organs)-> haemoglobin + oxygen
• Red blood cells have no nucleus, which means that they have more room for haemoglobin.
• In the centre of the cell, there are dimples. Scientists call this shape a biconcave disc. This shape gives the red blood cells a greater surface area so that oxygen diffuses in and out rapidly.

  
• White blood cells form part of the immune system for example by making anitbodies.
• White blood cells contain a nucleus. This contains DNA which encodes the instructions that the white blood cells need to do their job.
• Platelets are tiny fragments of cells and their job it to help the blood to clot.
• Donated blood has many used in medicine:

  • To replace blood lost during injury
  • Some people are given platelets extracted from the blood to help in clotting
  • Proteins extracted from blood can also be useful for example antibodies.
• In a blood transfusion, we have to make sure that the donated blood is the same blood type as the patient's. Otherwise the body's immune system will reject the blood and the patient could die.
• Lots of different diseases can be transmitted via blood. In the UK, blood is screened for infections so the risk is extremely low.