2.3 Heart and Blood Vessels

• Red Blood Cell


  transports O2 from lungs to body tissues

  contains haemoglobin which attaches to the oxygen to produce oxyhaemoglobin (which splits back enabling the oxygen to become free to diffuse)
• White Blood Cell


  Recognises and Responds to Pathogens:

  • Phagocytosis - engulfs pathogens.
  • Produces antibodies - binds onto pathogens and help destroy them.
  • Produces antitoxins - neutralises any toxins produced
• Platelets


  Small fragments of cells:

  • prevents blood from leaving blood vessels
  • aids in blood clotting
  • prevents entry of microorgansims
• Plasma

  Makes blood watery so it can flow:

  • transports all components and substances (nutrients, waste etc)
• RBC Characteristics

  • Extremely small - to pass through capillaries
  • Has no nucleus - more space for haemoglobin (maximises amount of oxygen that can be carried)
  • Bioconcave disk shape - creates a large surface area and allows for rapid diffusion of oxygen
• WBC Characteristics

  • Contain a nucleus
  • Ability to change shape - fit through the blood vessel walls into body tissues and to engulf harmful microorganisms.
  • Flexible cell membrane
• Arteries

  • Thick muscle tissue layer (strong)
  • Elastic tissues/fibres (stretch and recoil)
  • Lumen
  • Blood at a high pressure
• Capillaries

  • Huge cross sectional area
  • Blood at low pressure (flows slowly)
  • Extremely small
  • Single Cell thick
  • Permeable (allows for efficient diffusion)
  • Thin walls
• Veins

  • Thin layer of muscle tissue/elastic fibres (walls)
  • Blood at low pressure
  • Wider lumen - counteracts low pressure blood flow
  • Contains valves - prevents the backflow of blood
• Arteries

  Carries blood away from the heart.
• Capillaries

  Site of exchange (nutrients and oxygen with body tissues)

  Removes waste products
• Veins

  Carries blood back to the heart