Blood flow regulators in the arterial system.

Based on literature data and own results, the author describes the morphological peculiarities of arterial blood flow regulators. Terminology and opinions concerning these structures are discussed. Also pointed out is the importance of axially disposed smooth muscle cells, which --- together with the two lamina of internal elastic membrane, and the adventitia --- form a functional flow modulating system. Author concludes that the endothelial cushions are not pathological formations, but normal structural variations appearing during embryonal and perinatal life, as consequences of certain hemodynamic circumstances with local characteristics. Suggestions are given for re-estimation of classical data concerning the supposed blood flow regulating function of the embryo-fetal obliterated cords attached to vessels. New arguments are brought in support of the contribution of the close relations between large arteries and the surrounding osseous, muscular and fibrous structures to the control and modulation of the blood stream.