Blood

• • Blood is a tissue 
  • It is made of a liquid called plasma , which has three different components

  • Red blood cells 
  • White blood cells 
  • Platelets

  
• The role of plasma is to transport various chemical substances around the body:

  • It transports soluble digestion products (e.g. glucose) from the small intestine to other organs 
  • It transports carbon dioxide (produced by aerobic respiration) from the organs to the lungs to be breathed out 
  • It transports urea from the liver to the kidneys to be excreted in urine 
  • It also transports hormones and antibodies

  
• Role of red blood cells

  • Red blood cells transport oxygen from the lungs to the body cells which need it for respiration - to do this they have 4 adaptations:
  • They contain haemoglobin 
  • They have no nucleus 
  • They are shaped like a biconcave disk 
  • They are also very small

  
• How does haemoglobin allow red blood cells to transport oxygen from the lungs to the cells

  • Red blood cells contain the oxygen carrying molecule haemoglobin 
  • Haemoglobin binds to oxygen in the lungs to form the molecule oxyhaemoglobin 
  • The red blood cells than move to the organs / tissues where the oxyhaemoglobin releases the oxygen (and haemoglobin) - (which can now be transported to body cells)

  
• How does having no nucleus allow red blood cells to transport oxygen from the lungs to the cells

  Because the red blood cells have no nucleus , they have more room for haemoglobin (which can absorb oxygen to transport it from the lungs to tissues and cells)

  
• How does being small allow red blood cells to transport oxygen from the lungs the cells

  Red blood cells are very small , so they can fit through tiny capillaries

  
• How does being shaped like biconcave discs allow red blood cells to transport oxygen from the lungs to the cells

  Red blood cells are shaped like biconcave discs giving them a large surface area , that oxygen can diffuse in and out of quickly

  
• White blood cells roles and adaptations

  • White bloods cells form part of the immune system e.g. making antibodies 
  • White blood cells contain a nucleus - this encodes the instructions that the white blood cells need to do their job 
  • They help to protect the body against infection 
  • They can change shape , so they can squeeze out of the blood vessels into the tissues, or surround, engulf and destroy invading microorganisms
• Platelets

  • Platelets are fragments of cells  
  • They collect at wounds and trigger blood clotting
• Uses of donated blood in medicine

  • To replace blood lost during injury 
  • Some people are given platelets extracted from blood to to help in clotting 
  • Proteins extracted from blood can be useful for example in making antibodies
• Why the donated blood has to be the same as the patient's in a blood transfusion

  • In a blood transfusion, we have to make sure that the donated blood is the same as the patient’s 
  • Otherwise the body’s immune system will reject the blood and the patient could die
• Risk of infection from donated blood

  • Lots of different diseases can be transmitted via blood 
  • In the UK blood is screened so the risk is extremely low