Blood vessels

• The body contains 3 different types of blood vessels :

  1. Arteries
  2. Veins
  3. Capillaries
• Arteries

  Arteries carry blood Away from the heart. The blood in arteries is under high pressure - this increases each time the heart beats

  Arteries have thick walls containing muscle and elastic fibres - this allows arteries to:

  • stretch without bursting as blood is pushed through them
  • regain their shape afterword
• The first one is a arteries

  The second one is a vein

  The third one is a capillaries

  
• Veins

  Veins carry blood towards the heart .

  The blood in the veins is under the lowest pressure and is not pumped by the heart. Veins have :

  • Thinner walls than arteries
  • A larger lumen ( space inside )
  • Valves to prevent blood flowing backwards

  Blood is squeezed through the veins by the contractions of surrounding muscle
• Capillaries

  The capillaries are the smallest blood vessels and contain blood at low pressure.

  They form capillary beds - networks that supply blood to the body's tissue and organs

  Substances are exchanged between the blood in the capillaries and the cells around them.

  They are typically one cell wide , have thin walls - allowing substances to easily diffuse through them