Circulatory system
  1. Comparative anatomy
    1. open circulatory systems
      1. circulatory fluid indistinct from interstitial fluid
      2. low pressure
      3. examples: flat worm, insect
    2. closed circulatory systems
      1. blood distinct from interstitial fluid
      2. control of destination
      3. high pressure
      4. heart always has at least 2 chambers
        1. atrium
        2. ventricle
    3. examples of closed systems
      1. echinoderms
      2. vertebrate
        1. blood vessel construction
        2. capillary stucture different
        3. blood velosity, pressure shifts
          1. total cross-sectional area increases with smaller vessels
      3. fish
      4. amphibians
      5. reptiles
      6. mammals, crocodiles and birds
        1. all 4 chambered hearts (2 independent origins)
  2. cardiac function
    1. cardiac cycle
    2. cardiac output
      1. heart reat
      2. heart contractions
        1. coordination of contractions: sinoatrial node
  3. exchange of materials in tissues
    1. mostly occurs through diffusion, osmosis
    2. about 1% of water returns via lymphatic system
    3. larger molecules move via endo- or exocytosis
    4. pores only occur in kidney, liver
  4. Control of circulation (briefly)
    1. Regulation occurs at several different levels
      1. autoregulation: local control of capillary beds
      2. systemic control: CNS (central nervous system) and hormone control of larger vessels
      3. CNS control of blood pressure, composition
Study questions

1.  Compare the circulatory systems of one non-insect invertebrate, insects, fish, amphibians, reptiles and mammals.

2.  What is the phylogenetic argument for two independent origins of the four chambered heart?

3.   In the fish circulatory system, is arterial blood always oxygenated?  Is it always oxygenated in the mammalian circulatory system?

4.   Why would natural selection favor the evolution of a septum in the ventricle?  Under what circumstances (life styles) would you expect to find more fully developed septums, and under what reptilian "life styles" would you expect to find incomplete septa?  Would this necessarily correlate with "ancestral" and "derived" positions in the reptilian phylogeny?

5.  What other organ(s) in addition to the brain exert control on blood pressure?

See also:  Content review #2, 6;  Concept review #1