The Circulatory System (chp.5)

• The Circulatory System

  • Transport system of the body
  • composed of heart, blood & vessels
• 2 main circuits

  • Systemic (blood to body)
  • Pulmonary (blood to lungs)
• Functions of Blood

  • Transport: O2 & food to body cells, CO2 & urea from body cells, heat around body
  • Defence: platelets help prevent blood loss, white blood cells fight pathogens
• Composition of Blood

  • Plasma- liquid part, mostly water with dissolved chemicals
  • Red Blood Cells (corpuscles)- contain haemoglobins to O2- biconcave disc with no nucleus- made in bone marrow- v.v lots
  • White Blood Cells- fight infections by making antibodies or engulfing pathogens, made in bone marrow- less than red
  • Platelets- helps the blood to clot, fragments of cells- made in bone marrow, v. numerous
• Blood Vessels

  • Arteries- carries blood from heart, usually carries O2 (except pulmonary) have thick walls no valves
  • Veins- carry blood back to heart, usually doesn't carry O2 (except pulmonary) have thin walls & valves
  • Capillaries- brings blood from arteries to veins, have very thin walls to allow substances to pass through
• Heart


  Septum divides the heart into 2.

  Each side is then divided into small atria & larger ventricles
• Blood Flow

  1. Blood enters right atrium through vena cava
  2. Right atrium contracts & pushes blood into right ventricle
  3. This contracts & pushes blood to lungs via pulmonary artery
  4. Blood returns from lungs to left atrium via pulmonary vein
  5. Left atrium contracts & pushes blood into the left ventricle
  6. This contracts & pushes blood to body via aorta
• Heart

  • Average pulse is 72 beats per minute
  • Excercise increases pulse
  • To prevent don't smoke and eat less salt & fat foods