Circulatory system

• Circulatory System


  Heart, blood vessels, blood
• Double circulatory system


  • 2 loops
• Heart


  • Top chambers: atria (plural)
  • Bottom chambers: ventricles
  • The left side has thicker walls as it pumps blood around body
  • Valves prevent blood flowing backwards
• Blood flow


  1. Vena cava -> right atrium -> right ventricle -> pulmonary artery

  2. Pulmonary vein -> left atrium -> left ventricle -> aorta -> body
• Pacemaker


  • Located in right atrium
  • Generates small electrical impulses which cause the heart to contract
• Arteries


  • Muscular walls
  • Carry blood away from the heart
• Veins


  Carry blood to the heart
• Coronary arteries


  • Branch off aorta
  • Supply heart muscle with oxygen and nutrients
• Capillaries


  • Very small
  • Thin walls
  • Facilitate exchange of substances
• Arteries


  • Thick muscular/elastic walls and narrow lumen
  • Hold blood at high pressures
• Capillaries


  • Very small
  • Thin walls
  • Highly permeable - substances can easily diffuse. Lower blood pressure - flows slowly to allow blood time to exchange substances
• Veins


  • Thin walls, low blood pressure Biggest lumens
  • Contain valves to prevent backflow
• Blood components


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


  • Carry oxygen from lungs to tissues
  • Contain haemoglobin which binds to oxygen
  • Biconcave shape for large surface area No nucleus - more space for oxygen and haemoglobin
• White blood cells


  • Phagocytosis - engulf pathogens
  • Produce antibodies to destroy pathogens
  • Neutralise toxins
• Platelets


  • Small cell fragments with no nucleus
  • Stop bleeding and prevent microorganisms getting in cuts by causing clotting
• Plasma


  • Liquid part of blood
  • Carries nutrients, glucose, amino acids, hormones, proteins Straw coloured liquid - makes the blood watery so it can flow
• Most adults have around 5 litres of blood
• Blood transfusion


  • Adds volume
  • Provides red blood cells, antibodies, antitoxins
• Artificial blood 


  Mainly salt water

  Adds volume to blood

  No red blood cells, oxygen - can only replace a third of our blood
• Methods for replacing lost blood


  Blood transfusion

  Artificial blood