Microcirculation (part 2): «Functional responsibilities» of microcirculation system

   The article presents modern views on the main functions of microcirculation. In this aspect, two key positions are considered: the main blood flow through the microcirculatory vessels and the transcapillary exchange of fluid between the vascular and interstitial compartments.

   The purpose of the main microcirculatory blood flow is, first of all, to provide surrounding cells with oxygen, which is carried out by arteriolar diffusion of oxygen, as well as to remove carbondioxide and other metabolic products from the intercellular space.

   We describe a feature of capillary blood flow caused by speed fluctuations, which is associated with some changes in the deformability of leukocytes and their adhesive properties under the influence of various regulatory factors. An important characteristic of the microcirculation system is highlighted, which is the state of microhemorrheology, it depending on the pressure gradient, hematocrit and the ability of red blood cells to deform. The principle of fluid exchange between capillaries and tissue spaces is considered in the form of an updated version of the Starling–Landis equation and pressure distribution in the microcirculatory compartment of various capillary segments. Modern views on oxygen transport carried out by a complex intact cascade are presented. The main regulatory mechanisms in the microcirculation system are described in detail, including the three occurrence mechanisms of hyperpolarization of endothelial cells and vasodilation.

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