E9 Circulation and Transportation

Topic

Basic hemodynamics is modeled as a hydraulic system with three components: the heart, the blood vessels, and the tissues.

The first component is the heart: it acts as a pressure pump, generating the pressure difference that drives blood throughout the circulatory system.

The second component consists of the blood vessels: they act as tubes with variable resistance, widening or narrowing and thereby altering the resistance each vessel offers to the blood flow driven by the heart.

The third component is the tissues: they act as exchange sites where blood arriving via the blood vessels delivers oxygen and nutrients while collecting metabolic waste products from the tissues themselves.

With the heart driving blood flow, blood vessels regulating resistance to that flow, and tissues exchanging oxygen and nutrients, basic hemodynamics quantifies three variables: blood flow (the volume of blood passing through the circulatory system over a given period); pressure (the force with which blood pushes against vessel walls at any point in the system); and oxygen transport (the amount of oxygen actually delivered to the tissues via that blood flow).

The blood flow, pressures, and oxygen transport described by basic hemodynamics underpin muscle function during exercise and recovery: during exercise, muscles require increased oxygen transport to sustain the energy production needed to stave off fatigue; during recovery, they require that same oxygen transport to remain elevated long enough to replenish the energy substrates depleted during exercise.

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