CS - Blood

• Blood is a tissue. One of its jobs is to act as a huge transport system, there are 4 main things in blood
• The more red blood cells you've got, the more oxygen can get to your cells. At high altitudes there's less oxygen in the air - so people who live there produce more red blood cells to compensate
• Red blood cells carry oxygen

  
• The job of red blood cells is to carry oxygen from the lungs to all the cells in the body. Their shape is a biconcave disc - this gives a large surface area for absorbing oxygen

  
• Red blood cells don't have a nucleus - this allows more room to carry oxygen. They contain a red pigment called haemoglobin

  
• In the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin. In body tissues, the reverse happens - oxyhaemoglobin splits up in haemoglobin and oxygen, to release oxygen to the cells

  
• White blood cells defend against infection

  
• Unlike red blood cells, they do have a nucleus

  
• Some white blood cells can change shape to engulf unwelcome microorganisms, in a process called phagocytosis. Others produce antibodies to fight microorganisms, as well as antitoxins to neutralise any toxins produced by the microorganisms

  
• Platelets help blood clot

  
• Platelets are small fragments of cells. They have no nucleus. They help the blood clot up a wound - to stop all your blood pouring out and to stop microorganisms getting in

  
• Lack of platelets can cause excessive bleeding and bruising

  
• Plasma is the liquid that carried everything in blood

  
• Plasma is a pale straw-coloured liquid which carries everything in blood:

  • Red and white blood cells and platelets
  • Nutrients like glucose and amino acids. These are the soluble products of digestion which are absorbed from the gut and taken to the cells of the body
  • Carbon dioxide from the organs to the lungs
  • Urea from the liver to the kidneys
  • Hormones
  • Proteins
  • Antibodies and antitoxins produced by white blood cells