Blood Vessels

• The circulatory system consists of:

  • Blood
  • Blood vessels
  • Heart
• Blood transports:

  • Carbon dioxide
  • Oxygen
  • Nutrients
  • Waste products
  • Heat energy
  • Hormones
• 
  

  • Red blood cells (erythrocytes): Carry oxygen around the body, biconcave shape for a large surface area, no nucleus to have more space for haemoglobin
• Mammals and birds have closed circulatory systems, meaning the blood stays within the blood vessels as it circulates around the body
• Arteries:

  • Away from the heart
  • High pressure
  • Thick walls
  • No valves
• Capillaries:

  • From arteries to veins
  • Lower pressure
  • Very thin walls
  • No valves
• Veins:

  • Towards the heart
  • Low pressure
  • Thinner walls than arteries
  • Valves
• • White blood cells (leukocytes): Defend against disease, produce antibodies
• • Platelets: Fragments of cells, allow blood clotting
• • Plasma: The liquid component of blood, carries other components of blood and dissolved chemicals