Circulatory System

• heart

  it is a pumping organ that keeps the blood flowing around the body
• pulmonary artery takes blood to heart
• aorta takes blood to body
• • blood flows in the two atria from the vena cava and pulmonary vein
  • atria contract pushing blood into ventricles
  • ventricles contract forcing blood into pulmonary artery and aorta out of the heart
  • blood then flows to organs through arteries and returns through veins
  • atria fill again and cycle restarts
• blood vessels

  are designed for their function
• 3 types of blood vessels

  arteries

  veins

  capillaries
• arteries

  • take blood from heart
  • walls are strong , elastic and thick
  • carry blood at high pressure
  • have thick layers of muscle
• veins

  • return blood to heart
  • large lumen - more room
  • thin walls - blood to travel easily
  • valves - prevent backflow
  • blood is taken at low pressure
• capillaries

  • supply food and oxygen
  • tiny, permeable walls - diffusion
  • very small lumen
  • thin walls
• blood

  is a tissue and acts as a huge transport system
• red blood cells

  • transport oxygen to cells
  • contain haemoglobin
  • no nucleus & biconcave shape for larger surface area
• white blood cells

  • large & contains a nucleus
  • forms body's natural defence
  • forms y-shaped antibodies
  • phagocytosis engulfs and digests bacteria/viruses
• platelets

  • small fragments of cells
  • no nucleus
  • makes blood clots/scabs
  • converts fibrinogen to fibrin
• plasma

  • yellow coloured liquid
  • carries blood cells
  • transports urea from liver to kidney
• pacemaker

  • used for irregular heartbeat
  • located in the right atrium
  • small electric impulses spread out to muscle cells to contract
• heart diagram

  A) pulmonary artery

  B) aorta

  C) pulmonary vein

  D) left atrium

  E) left ventricle

  F) right ventricle

  G) right atrium

  H) vena cava