RESUMO
The human body consists of various systems (blood, tissues, extracellular fluid, intracellular contents) separated by biological membranes. Physiological barriers ensure the physico-chemical composition of the internal environment remains constant and protects the body from environmental changes. The permeability of the histohematic barrier depends on the concentration of substances in the blood, the body's condition, external influences, and a number of other reasons caused by stimuli coming from the external or internal environment. Information about the state of the regulatory systems of the body has its effect on specific chemoreceptors, which leads to the emergence of local and general physiological and biochemical processes. According to their localization, they distinguish between the hematoencephalic, hemato-placental, hemato-ophthalmic, and hemato-salivary barriers. Recently, the hematosalivary barrier, through which the selective entry of substances from the blood into the oral fluid is carried out, has taken a special place in the study. Its functioning depends on the processes occurring in the body, which is carried out by selective permeability for substances that determine the composition of the main internal environment of the body - blood. Hematosalivary barrier is an important link in maintaining homeostasis, which is reflected in the metabolic parameters of oral fluid.
