Perihemorheology: the bridge between the vessel-blood organ and the organs it penetrates.

Perihemorheology concerns the rheology of fluids and structures in the perivascular spaces. Furthermore, the term refers to the exchanges of rheological processes between the vessel-blood organ and its surrounding tissues, as well as in reverse. In 1960, the vessel wall and the circulating blood were considered by the author as an entity which in 1981 he postulated as an organ, named the 'vessel-blood organ', penetrating all other organs. This communication is not a survey but is intended to stimulate biomedical thinking regarding the importance of perihemorheology. The significance of the endoendothelial fibrin(ogenin) lining (EEFL) and fibrin(ogenin) as constituent of the interendothelial cement and the basement membrane in relation to perihemorheology is stressed. The role of albumin in the exchanges between hemorheology and perihemorheology is discussed. The protein content, as found by Witte, in the perivascular spaces as compared to the blood is emphasized regarding the importance of interrelations between the vessel-blood organ and rheological processes in the perivascular spaces. Recent studies, particularly by Laurent and his group, pertaining to hyaluronan in perivascular spaces and the blood demonstrate also the importance of the interrelationship between hemorheology and perihemorheology. The term 'blood-brain barrier', considered no longer to be adequate, is replaced by the term 'basement membrane-brain barrier'. It is proposed that the basement membrane of the vessel-blood organ penetrating the brain may contain certain constituents, unknown thus far, and may have a different structure from the basement membrane of the vessel-blood organ penetrating organs other than the brain.