Components of blood

• Roles of blood:

  • Helps defend the body against microorganisms which cause disease
  • Helps control the body temperature
• Blood contains types of cells:

  • Red blood cells
  • White blood cells
  • Platelets
• Plasma:

  • Blood contains red blood cells, white blood cells and platelets which are carried in a fluid called plasma
  • Within the plasma, dissolved substances like oxygen and glucose, urea and carbon dioxide will also be transported around the body
  • Plasma is a yellow colour, blood is only red because of the haemoglobin in red blood cells
• Red blood cells - Carry the oxygen from the air in our lungs into our respiring cells
• White blood cells - Form part of the immune system. Some white blood cells (lymphocytes) produce antibodies or antitoxins and others (phagocytes) engulf and digest invading microorganisms
• Platelets are small fragments of cells without a nucleus that help to clot blood

  • The clotting process forms a network of fibres that traps more platelets and red blood cells to form a scab which protects the new skin as it grows underneath
  • Scabs also prevent microorganisms from getting into the cut, so it stops infection