Architecture of the Circulation, Dr. D. Penney



Circulation Time

"Average time taken for a RBC (or injected dye*) to traverse the systemic & pulmonary circulations, and return to the starting point".

Circ. t (sec.) = Vasc. bed vol. between A & B (ml) / vol. flow, A to B (ml/sec)

For example:

Coronary route =10 sec.
Some routes = several minutes (extensive venous sinuses spleen, etc.)
Body average = 40 -60 sec. (vol. of the card. output circulated approx. once per min.)

Effects on:

  • Circulation time is decreased by exercise, arteriovenous shunting, reduced venous pooling.

  • Most of time is spent in the veins; thus, circulation time is more dependent on what happens in the veins than in the arteries, arterioles (i.e. vaso - venomotion)




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