[The human placenta and its normal role and in pathology]

The information on placenta formation, development and structure in health and disease, as well as the role of the placenta as a unique organ which ensures the fetal growth and development during pregnancy is given on the basis of the literature and author's data. Attention is drawn to the formation of the compensatory-adaptive reactions as a complex dynamic process whose manifestations are considered on the subcellular, cellular and tissue levels. Connection between the morphological equivalents of the compensatory mechanisms and the process of maturation of placental barrier structural elements is shown. Determining the character of maturation disorders in combination with the placenta damage allows one to suggest, by means of clinico-anatomical analysis, a particular maternal pathology as the most probable cause of the unfavourable intrauterine conditions of the fetal development. A working classification of placental insufficiency resulting mainly from the disturbance of the compensatory-adaptive reactions is proposed.