Heart

• Double circulatory system


  When the blood passes through the heart twice on one complete circuit of the body
• Double circulatory system


  • Found in all mammals, birds and reptiles
  • Has two parts: pulmonary system and systemic system
• Single circulatory system


  When the blood passes through the heart only once on a complete circuit

  
• Single circulatory system


  • Blood just carries on around the fish's body
  • Blood travels much more slowly to a fish's body organs than it does in a mammal
• Heart


  Pump that keeps blood flowing through the vessels
• Heart


  • Valves in the heart and blood vessels make sure the blood flows in the right direction

  
• Oxygenated blood


  Blood in the left-hand side of the heart that has come from the lungs, containing oxygen
• Deoxygenated blood


  Blood that has been used by the body's cells and is low in oxygen
• Atria


  The two upper chambers of the heart
• Ventricles


  The two lower chambers of the heart
• Septum


  Separates the chambers on the left-hand side from the right-hand side
• Left atrium


  Receives blood from the pulmonary veins, which come from the lungs
• Right atrium


  Receives blood from the rest of the body arriving through the vena cava
• Blood flow through the heart

  1. Flows from atria to ventricles

  2. Ventricles pump blood out of the heart
• Ventricles


  • Have much thicker, more muscular walls than the atria
• Left ventricle


  Has an especially thick wall of muscle to pump the blood all around the body
• Right ventricle


  Pumps blood to the lungs, which are very close to the heart
• Atrioventricular valves


  One-way valves between the left atrium and ventricle
• Atrioventricular valves


  Stop blood flowing from the ventricles back to the atria
• Coronary arteries


  Blood vessels on the outside of the heart that supply blood to the heart muscle

  
• Coronary heart disease (CHD)

  If a coronary artery gets blocked, the cardiac muscle run short of oxygen and cannot contract, causing a heart attack or cardiac arrest
• Factors which increase the risk of CHD

  • Smoking cigarettes
  • Diet
  • Obesity
  • Stress
  • Genes
• Heartbeat


  • 60 - 75 times a minute (resting)
  • Pulse rate is the same as the heart rate
• Exercise


  Heart beats faster to deliver more blood and oxygen to the muscles
• Pacemaker


  Patch of muscle in the right atrium that controls the heart beats by sending electrical signals
• Arteries


  • Carry blood away from the heart
  • Small lumen, relatively narrow
  • Thick and strong outer wall
  • Smooth lining
  • Thick layer of muscles and elastic fibre
• Veins


  • Return blood to the heart
  • Fairly thin outer wall
  • Smooth lining
  • Thin layer of muscles and elastic fibres than arteries
  • Large/wide lumen, contains valves

  
• Capillaries


  • Very small lumen, very narrow, just wide enough for a red blood cell to pass through
  • Wall made of single layer of cells
  • Very thin, only one cell thick
• Plasma


  Liquid part of the blood, mostly water containing many substances in solution
• Functions of plasma


  • Liquid medium in which cells and platelets can float
  • Transport carbon dioxide in solution
  • Transport nutrients in solution
  • Transport hormones in solution
  • Transport heat
  • Transport antibodies
• Red blood cells


  Made in the bone marrow, contain haemoglobin which carries oxygen, biconcave discs with no nucleus
• Functions of red blood cells

  • Transport oxygen
  • Transport small amount of carbon dioxide
• Red blood cells


  Small size and shape gives them a large surface area to volume ratio, enabling fast diffusion of oxygen and carbon dioxide
• White blood cells


  Have a nucleus, can move around and squeeze out of capillaries
• Functions of white blood cells

  • Engulf and destroy pathogens
  • Make antibodies
• Platelets


  Small fragments of cells with no nucleus, help in blood clotting
• Blood clotting stops pathogens getting into the body through breaks in the skin and prevents too much blood loss