circulatory system

• what are the three components of the circulatory systems?

  blood

  heart

  blood vessels
• open system (e.g. insects)

  
• closed system (e.g. mammals & fish)

  
• single circulatory system: blood passes through the heart once for each cycle around the body; oxygenated and deoxygenated blood mix
• double circulatory system: blood passes through the heart twice for each cycle around the body; oxygenated and deoxygenated blood are separate
• what keeps fish active despite a single circulatory system?


  this:

  • countercurrent exchange
  • low metabolic demand
  • buoyancy -> bodyweight is supported by water
• how comes fish have low metabolic demand?


  they don't require thermoregulation as water has a high specific heat capacity so the temperature is mainly stable
• amphibians have three chambered heart with 2 atriums and 1 ventricle
• single circulatory system:

  • blood passes through two sets of capillaries before returning to the heart
  • one circulation - systemic
  • heart has no septum
  • heart has two chambers: 1 atria & 1 ventricle
  • lower blood pressure
  • less efficient
• double circulatory system:

  • blood passes through one set of capillaries before returning to the heart
  • two circulations - pulmonary and systemic
  • heart has a septum - separating oxygenated and deoxygenated blood
  • heart has four chambers: 2 atria & 2 ventricles
  • higher blood pressure
  • more efficient