RESUMEN
Pineal gland (PG), or epiphysis, is involved in the organization of biological rhythms and adaptive reactions of the organism through the hormone melatonin. It is shown that various factors can influence the morphology and functional activity of the gland. Calcified concretions (corpora arenacea, brain sand) are unique biomineral structures of the PG, the causes of the formation and possible functional significance of which remain unclear until now. Currently, concrements have been found in several species of birds, in many mammals as well as humans; they are absent in fish, amphibians and reptiles. In this review, we have collected the available literature data on the composition, mechanisms of formation, and the possible factors affecting the accumulation of concretions in the epiphysis. Despite the fact that the generally accepted point of view is the age-dependent nature of the accumulation of pineal calcium deposits, the available data on the PG mineralization lead to the conclusion that, most likely, there is a multifactorial mechanism for the formation of concrements. In addition, the nature and crystallinity of the inorganic tissue of the pineal concretions suggest that corpora arenacea is rather a regulated and physiological than pathological type of petrification. The existence of contradictory data on the connection between the formation of brain sand and the change in the functional activity of the PG during seasonal endocrine changes and in the process of aging makes the study of deposits as the necessary and requiring in-depth investigation.
