Local control of blood flow

One of the important characteristics of the microcirculation is that it affords each tissue the ability to control its own local blood flow in proportion with its own requirements62.

This needs-based system of perfusion is vital. Continuous luxury-perfusion to all tissues would have greatly exceeded the mechanical capabilities of the heart. Actually, blood flow in each tissue is usually adjusted to the minimum level which satisfies its requirements. Thus, tissues never lack nutrients and the mechanical workload of the heart is kept at a minimum appropriate level.

Control on local blood flow can be divided into two phases : immediate and long-term control. Immediate control is ensured by swift changes in the diameters of the arterioles and of the pre-capillary sphincters which take place within seconds or minutes to make sure the adequate local blood flow is maintained. Long-term control is responsible for changes in blood flow over periods of several days, weeks or even months. Generally the long-term changes involve the increase or decrease of the number (angiogenesis) and calibre of the blood vessels providing nutrients to the tissues.

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