Blood

• Plasma Is the liquid that carries everything in blood
• Plasma transports :

  • Soluble digestion products from small intestines to other organs
  • carbon dioxide (from aerobic respiration) organs to lungs to be breathed out
  • 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 a pigment called haemoglobin

  • In the lungs haemoglobin combined with oxygen to form oxyhemoglobin
  • red blood cells travel to organs where oxyhemoglobin will release oxygen to the cells
• Red blood cells have no nucleus, which means that they have more room for haemoglobin
• Red blood cells shape is a biconcave disc, gives them a large surface area for rapid diffusion of oxygen
• White blood cells defend against infections
• White blood cells contain a nucleus .
• Some white blood cells can change shape to get rid of unwanted microorganisms (phagocytosis)
• some white blood cells produce antibodies to fight microorganisms, as well as antitoxins to neutralise any toxins produced by the microorganisms
• Platelets are small fragments of cells that help blood to clot at a wound, to stop all your blood pouring out and to stop microorganisms getting in

  Lack of platelets can cause excessive bleeding and bruising