Architecture of the Circulation, Dr. D. Penney

Architecture of the circulation - Summary

  • Two pumps in series, each through own resistance in connecting vessels ('right heart/left heart', common septum and pacemaker).

  • Blood pressure higher on arterial side, lower on venous; thus arterial resistance greatest (ca. 40% in arterioles, 30% capillaries).

  • Symmetrical arrangement of components -
      - decreasing, then increasing diameter
      - decreasing, then increasing length
      - increasing, then decreasing number
      - increasing, then decreasing x - sectional area
      - increasing, then decreasing surface area

  • Pattern of number and surface area consistent with exchange function.

  • Pattern of x-sectional area dictates decrease, then increase in blood flow velocity (i.e. reciprocal relationship).

  • Blood volume greatest on venous side (55 - 65%), nil in capillaries.

  • Blood O2 concentration; high on arterial side, low on venous (a-v O2 difference).

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